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:  RCISES 


COLUMBIA    UNIVERSITY 
DEPARTMENT     OF     PHYSIOLOOY 
THE    JOHN    G.   CURTIS    LIBRARY 


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UNIVERSITY  COLLEGE  COURSE, 


PEACTICAL  BXEECISES 


PHYSIOLOGY 


J.    BURDON   SANDERSON,    M.D.,    LL.D.,    F.R.S. 

JODRELL    PROFESSOR    OF    PHYSIOLOGY    IN    UNIVERSITY    COLLEGE,    LONDON. 


WITH    THE    CO-OPERATION    OF 


F,  J.  M.  PAOE,  B.SC,  F.C.S.,  W,  NORTH,  B.A.,  F.C.S.,    AND  AUG.  WALLER,  M.D. 


PHILADELPHIA 
P.  BLAKISTON,  SON  &  Co.,  1012  WALNUT  STREET 

1882 


9?44 


PREFACE. 


The  following-  exercises  are  intended  to  serve  as  a  guide  to 
the  Practical  Courses  which  are  given  in  the  Physiological 
Department  of  this  College.  Part  III.  comprises  the  Chemi- 
cal Exercises  relating  to  Food  Stuffs  and  Animal  Liquids 
which  are  performed  by  every  Student  in  the  Class  Room,  in 
the  ordinary  course  of  Practical  Physiology.  These  Exer- 
cises were,  for  the  most  part,  originally  arranged  by  Mr. 
Page.  They  have  been  used  by  many  hundreds  of  Students 
and  have  been  found  to  work  well.  Part  IV.  contains  direc- 
tions for  the  more  detailed  practical  study  of  the  same  subjects. 
In  the  preparation  of  these,  I  have  had  the  assistance  of  Mr. 
North  who  has  used  them  in  the  Practical  Instructions  which 
he  has  given  here.  The  exercises  in  Part  I,  relate  to  the 
Physiology  of  Muscle  and  Nerve.  In  selecting  them  great 
care  has  been  taken  to  include  nothing  which  cannot  be  suc- 
cessfully carried  out  by  the  Student.  Many  of  the  exercises 
have  been  contrived  by  Dr.  Augustus  Waller,  who  has  de- 


U  PREFACE, 

voted  much  time  and  thought  to  the  simplification  of  methods. 
The  Demonstrations  in  Part  IV.  relate  to  various  subjects. 
These  are  separated  from  the  rest  of  the  course,  on  the  ground 
that  they  do  not  admit  of  being  performed  by  each  student 
for  himself. 


UNIVERSITY  COLLEGE  COURSE 


PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 


Part   I. 


PRACTICAL    EXERCISES    RELATING   TO   THE   PHY- 
SIOLOGY OF   MUSCLE    AND   NERVE. 

1.  Make  electrodes  as  follows : — Prepare  two  straight,  moder- 
ately thick  wires  about  four  inches  long.  Taper  each  to  a 
blunt  point  at  one  end.  Solder  to  the  opposite  end  of  each  a 
length  of  thin  wire.  Cover  each  with  a  thin  layer  of  packing 
wax.  Prepare  two  three-inch  lengths  of  glass  tubing  (which 
should  be  thick  walled  and  of  narrow  bore).  Warm  them, 
and  introduce  the  wires  so  that  their  points  project  half  an 
inch.  Bind  the  tubes  together  for  convenience  of  handling 
and  bare  the  wires  by  scraping  the  wax  off  near  the  point  on 
one  side. 

2.  Put  up  a  Daniell  cell.  The  positive  element  is  a  well 
amalgamated  zinc  rod  immersed  in  ten  per  cent,  sulphuric  acid 
contained  in  a  porous  cell ;  the  negative  element  is  a  copper 
cylinder  containing  a  solution  of  sulphate  of  copper.  Put  a 
wire  in  each  binding  screw.  The  end  of  the  wire  attached 
to  the  zinc  (negative  wire),  is  called  the  cathode;  that  at- 
tached to  the  copper  (positive  wire),  the  anode. 

B 


2      PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

3.  PitV''  a  frog  and  prepare  a  sciatic  Jierve  without  dividing  it, 
(See  Hdb.  p.  343).  In  the  process  the  gastrocnemius  should 
not  have  twitched. 

4.  Connect  the  electrodes  with  a  Daniell  cell,  interposing  a  key  in 
the  circuit.  Contraction  follows  make,  or  make  and  break.  It 
does  not  continue  during*  passage  of  current.  The  excita- 
bility of  the  nerve  is  increased  by  division  or  injury. 

5.  Arrange  cell  and  coil  for  single  shocks,  i.e.,  join  the  ends 
of  the  battery  wires  to  the  two  top  screws  of  the  du  Bois'  induc- 
tion apparatus,  in  which  the  primary  wire  ends,  interposing  a 
key  by  which  the  current  is  made  and  broken  at  will.  Grad- 
ually sliding  the  secondary  towards  the  primary  coil,  observe 
that  the  break  shock  is  first  responded  to,  then  the  make. 
Note  the  distance  of  secondary  from  primary  coil  at  which 
you  first  get  contraction  in  each  case. 

6.  Arrange  cell  and  coil  for  repeated  shocks  (faradisation), 
by  bringing  the  battery  wires  to  the  two  screws  A  and  E,  Fig.  i . 
The  circuit  now  includes  the  vibrating  hammer  or  automatic 
interrupter.  On  closing  the  current,  the  hammer  is  drawn 
down  and  causes  a  break;  the  current  ceasing,  the  hammer 
is  released,  and  contact  is  restored  by  the  spring.  You  thus 
obtain  a  succession  of  make  and  break  induction  currents  in 
alternately  opposite  directions.  Prepare  the  second  sciatic 
nerve,  and  observe  that  faradisation  produces  continuous 
muscular  contraction  or  tetanus,  which  may  be  due  either 
to  the  series  of  break  excitations,  or  to  the  double  series  of 
strong  break  excitations  and  weaker  ones  at  make.  Note  the 
distance  at  which  you  first  get  contract4on. 

7.  To  obtain  successive  make  and  break  excitations  of 
nearly  equal  intensity,  arrange  for   single   shocks   as  in  5. 

*  In  future  experiments  it  is  assumed  that  pithing  is  performed  as  a  mat- 
ter of  course. 


METHODS    OF    EXCITATION. 


X   "T^ 


JFi^ff.l 


But  in  addition,  connect  the  two  ends  of  the  primary  coil 
(the  top  binding-  screws),  by  an  extra  derivation  or  "short 
circuiting"  wire  broken  by  a  key.  By  closing  this  key,  the 
current  in  the  primary  coil  is  diminished  by  derivation,  and  in- 
creased to  the  same  amount  when  it  is  opened.  The  diminu- 
tion and  increase  give  rise  to  induction  currents,  of  which, 
the  directions  are  opposed  like  those  produced  by  make  and 
break.  Both  of  them  are  cat.  par.  weaker  than  the  make 
induction  current,  and  they  are  sensibly  equal  to  each  other  in 
their  excitatory  effects. 

8.  Helmholtz'  Modification  of  the  Induction  Apparatus.— 
When  it  is  necessary  in  faradising  that  the  excitatory  effects 
of  the  make  and  break  shocks  should  be  equal,  the  apparatus 
is  arranged  as  in  fig-.  2.  Connect  the  battery  wires  as  in  6. 
Bridge  the  interrupter  by  a  wire  extending-  from  B  to  C. 
Raise  the  upper  contact  screw  C  out  of  reach,  and  bring-  the 

62 


PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 


(3^ 


lower  (F)  within  reach  of  the  spring".  Here,  as  in  the  other 
case,  the  current  in  the  primary  coil  diminishes  by  deriva- 
tion, when  the  descending  hammer  touches  F;  increases  to 
the  same  amount  when  it  rises,  but  is  never  broken. 

9.  Use  of  the  du  Bois  key.  Before  proceeding  further,  note 
that  a  key  may  be  used  for  throwing  a  current  into  or  cutting- 
it  off  from  a  nerve  or  other  excitable  structure  in  \.\\o  ways, 
viz.,  (i)  in  such  a  way  that  when  it  is  closed  the  current  is 
made,  when  it  is  opened  the  current  is  broken ;  or  (2)  so  that 
when  the  key  is  closed  it  acts  as  a  bridge,  by  which  so  large 
a  proportion  of  the  current  is  derived,  that  it  in  effect  vanishes 
in  the  part  of  the  circuit  beyond  the  bridge. 

In  using  induction  currents  for  excitation,  always  employ 
the  second  method. 

10.  To  Cut  off  the  Make  or  Break  Shock.— For  this  pur- 
pose a  key  may  be  introduced  into  the  secondary  circuit,  by 


METHODS    OF    EXCITATION.  5 

which  it  can  be  closed  or  opened  at  will  during  make  or 
break  of  the  primary  current;  or  this  may  be  effected  auto- 
matically, by  fixing-  an  ebonite  rod  made  for  the  purpose  to 
the  hammer,  so  as  to  prolong  it  for  about  an  inch.  The  rod 
carries  at  its  end  a  platinum  wire  in  the  shape  of  an  inverted 
U.  The  two  limbs  of  the  q  are  of  such  length  that  they 
dip  into  two  pools  of  mercury,  which  are  severally  connected 
with  the  ends  of  the  secondary  coil.  Consequently,  when  the 
hammer  descends,  the  [\  bridges  the  two  pools,  so  that  the 
secondary  coil  is  short  circuited.  As  at  the  moment  of  break 
of  primary  circuit  the  hammer  is  down,  the  break  shock  is 
thus  cut  off.  If  the  pools,  instead  of  being  connected  as 
above,  are  interpolated  in  secondary  circuit,  the  make  shock 
is  cut  off. 


II.  Physiological  Proof  of  the  Break  Extra  Current.— 
The  extra  current  is  the  current  produced  in  a  coil  by  the 
inductive  influence  of  contiguous  turns  on  each  other,  when  a 
voltaic  current  commences  or  ceases  through  the  coil  ;  its 
direction  is  against  that  of  the  battery  current  at  make,  with 
it  at  break.     Establish  connections,  as  in  Fig.  3,  placing  the 


b  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

electrodes  on  the  tongue.  Close  the  key,  A,  so  that  the 
current  is  cut  off  from  the  coil.  Observe  that  opening  and 
closing  the  current  by  the  key,  B,  produces  little  or  no  appre- 
ciable effect.  Now  open  the  key.  A,  so  that  the  current 
passes  through  the  coil.  Opening  the  key,  B,  gives  rise  to  a 
Strong  effect  which  is  due  to  the  break  extra  current. 

12.  Introduce  a  second  pair  of  electrodes  into  the  current  of 
the  battery  and  primary  coil,  arranged  as  in  5,  and  apply 
them  to  the  tip  of  the  tongue.  Observe  the  effect  of  making 
and  breaking  the  current,  first  with,  and  then  without  the 
core.  Similarly  compare  these  effects  with  those  of  the  in- 
duced make  and  break  currents  in  the  secondary  wire. 

13.  Unipolar  Excitation.— Connect  one  electrode  with  the 
secondary  coil,  and  apply  it  to  the  nerve.  If  the  preparation 
is  completely  insulated,  there  should  be  no  response  to  make 
or  break.  If  the  insulation  is  destroyed  by  touching  the  pre- 
paration, or  otherwise,  contraction  occurs. 

It  is  to  avoid  unipolar  excitation  that,  as  a  rule,  the  induc- 
tion circuit  is  directed  to  be  thrown  in  and  out  by  using  the 
key  as  a  bridge  (See  9).  Unipolar  excitation  is  more  apt  to 
occur  with  the  break  shock  than  with  the  make,  in  conse- 
quence of  the  greater  intensity  of  the  former.  Consequently, 
it  is  avoided  by  using  Helmholtz'  modification.  Prove  this  by 
experiment. 

14.  Make  and  record  observations  on  the  comparative 
excitability  of  nerve  and  muscle  as  follows  : — Note  the  ap- 
proximation (in  centimeters)  of  the  secondary  to  the  primary 
coil  which  is  required  to  obtain  a  response  (i)  to  the  make 
induction  shock ;  (2)  to  the  break ;  (3)  to  faradisation,  with 
the  nerve  undivided.  Then  repeat  the  observation  after 
dividing  the  nerve.  Compare  these  effects  with  those  ob- 
served when  the  electrodes  are  applied  directly  to  the  muscle. 


METHODS    OF    EXCITATION.  7 

15.  The  Bitter- Valli  Law  (H.'"*  p.  334).  Prepare  a  sciatic 
nerve  without  severing  it.  Compare  the  excitability  to  fara- 
disation  of  the  different  parts  of  the  nerve,  placing-  the 
electrodes  (i)  at  the  ischium;  (2)  close  above  the  knee:  In 
about  an  hour  repeat  the  experiment,  using-  the  same  nerve. 
Then  sever  the  nerve  near  its  orig-in,  and  so  repeat  the 
experiments.  Note  the  results  in  each  case.  Finally,  repeat 
the  observations,  using-  the  nerve  of  the  opposite  limb. 

16.  The  Rheochord.— Whenever  very  weak  voltaic  currents 
are  required,  we  use  the  Rheochord.  The  simplest,  and  most 
convenient  form  is  a  long-  wire  of  German  silver,  of  about  20 
Ohms  resistance,  which,  for  convenience  of  space,  is  wound 
on  glass  pegs  which  are  fixed  at  equal  distances  in  two  rows 
at  opposite  ends  of  a  well-varnished  mahogany  board.  The 
wire  is  then  divided  into  as  many  equal  lengths  as  there  are 
pegs.  On  the  board,  underneath  the  first  length  is  a  scale, 
each  division  of  which  is  y-^-„  of  the  whole  length  of  the  wire. 
The  wire  ends  in  two  blocks,  A  and  B,  each  of  which  has  two 
binding  screws.  In  use,  the  battery  wires  are  connected  with 
these  two  blocks.  One  of  them  (the  one  from  the  graduated 
end  of  the  rheochord  wire)  also  receives  the  wire  of  the  second 
electrode.  The  other  electrode  wire  is  brought  to  a  sliding 
block,  by  which  contact  can  be  established  with  the  rheochord 
wire  at  any  distance  from  A.  In  this  arrangement,  the  cur- 
rent through  the  nerve,  or  other  structure  to  which  the  elec- 
trodes are  applied,  is  proportionate  to  the  length  of  ivire  between 
the  slider  and  the  block.  This  relation  would  not  hold  good 
were  it  not  that  the  resistance  of  the  nerve  is  always  very 
great  as  compared  with  that  of  the  wire. 

17.  Polarisation  of  Electrodes.— Place  a  pair  of  electrodes 
under  the  sciatic  nerve,  and  join  them  by  a  key,  and  satisfy 

•  In  this  and  other  similar  references,  H.  stands  for  Hermann,  and  F.  lor 
Foster. 


8  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

yourself  that  opening-  and  shutting  the  key  gives  no  contrac- 
tion. Connect  the  two  wires  of  a  Daniell  with  each  side  of 
the  same  key,  which,  therefore,  bridges  the  current.  Allow 
the  current  to  pass  through  the  nerve  for  a  few  instants  by 
opening  the  key,  remove  the  battery  wires,  leaving  the  elec- 
trode wires  attached  to  the  open  key.  Close  the  key,  the 
muscle  will  contract,  the  electrodes  having  been  polarised  by 
the  previous  current.  Leave  the  key  closed  for  a  few  instants; 
open  and  again  close,  the  muscle  will  not  contract,  polar- 
isation of  the  electrodes  having  subsided  during  closure  of 
circuit.  This  gives  a  reason  for  using  the  key  as  a  bridge 
to  cut  off  the  constant  current.  If,  in  experiments  on 
the  law  of  contraction  (See  §  32)  it  is  used  to  make  and 
break  the  current,  it  will  be  noticed  that  at  each  successive 
closure  the  contractions  diminish  as  polarisation  augments. 

18.  Unpolarisable  Electrodes.  (H,  287,  F.  55),  The  form 
in  common  use  consists  of  (i)  a  smooth,  amalgamated*'  zinc  rod 
dipping  into  (2)  a  saturated  solution  of  zinc  sulphate,  with  which 
the  tissue  is  electrically  continuous  by  (3)  a  plug  of  china  clay 
made  into  a  paste  with  saline  solution  -75  per  cent.  Threads 
may  be  used  to  connect  the  plug  with  the  tissue.  Such  elec- 
trodes are  of  high  resistance.  (For  the  method  of  testing 
them  with  reference  to  their  freedom  from  polarity,  See  I.,  17). 

19.  Galvani's  Experiment.— Connect  two  dissimilar  metals, 
e.g.,  zinc  and  copper  wire;  and  apply  their  points  to  a  nerve,  or 
one  point  to  a  nerve,  the  other  to  any  part  of  the  frog;  con- 
traction occurs  at  make,  or  if  the  preparation  is  very  excit- 
able, at  make  and  break. 

•  To  make  amalgamating  liquid  for  electrodes,  dissolve  with  gentle  heat 
3  c.c.  of  mercury  in  a  mixture  of  50  c.c.  nitric  acid,  and  150  c.c.  of  hydro- 
chloric acid.  Dilute  this  liquid  for  use  with  its  own  volume  of  hydrochloric 
acid,  and  eight  times  as  much  water. 


METHODS    or    EXCITATION.  Q 

20.  The  Contraction  without  Metals.— Prepare  a  nerve- 
muscle  preparation,  choosing-  a  vigorous  and  lively  frog. 
Lay  the  nerve  on  the  muscles  of  the  other  limb  stripped  of 
its  skin.  The  muscle  of  the  preparation  contracts  because 
different  parts  of  the  surface  with  which  the  nerve  is  suddenly 
brought  into  contact  are  at  different  potentials. 

21.  The  Secondary  Twitch.  (F.  p.  59,  H.  290).  Prepare 
the  sciatic  nerve  of  one  limb  of  a  vigorous  frog,  and  prepare 
a  nerve-muscle  preparation  from  the  other  limb.  Strip  the 
skin  off  the  first  limb,  and  lay  the  nerve  of  the  preparation  on 
the  gastrocnemius.  Apply  various  stimuli  to  the  first  nerve, 
both  muscles  contract;  the  secondary  muscle  contracts  be- 
cause its  nerve  is  stimulated  by  the  sudden  electrical  changes 
which  accompany  the  contraction  of  the  primary  muscle. 

22.  The  Paradoxical  Contraction.  (H.  343,  346).  Dissect 
out  one  of  the  two  main  divisions  of  the  sciatic,  and  divide  it 
at  its  periphery.  Galvanic  excitation  of  the  peripheral  part 
of  the  divided  branch,  gives  rise  to  contraction  of  the  muscles 
supplied  by  the  other  branch.  The  second  nerve  is  stimulated 
by  the  electrotonic  alteration  of  the  first  nerve. 

23.  Action  of  Curare.  (F.  p.  38).  la  )  Inject  one  drop  of 
curare  solution  (i  per  cent.),  having-  stopped  the  circulation  of 
one  limb  by  a  ligature  from  which  the  nerve  is  excluded.  In 
a  few  minutes,  test  muscle  and  nerve  of  both  limbs.  Both 
react  on  the  ligatured  side ;  on  the  other  side,  muscle  reacts, 
nerve  does  not. 

(b.)  Proceed  as  before,  but  use  the  ordinary  dose  of  curare, 
I  to  2  drops  of  o*  I  per  cent,  solution,  and  wait  longer.  In- 
ject I  drop  of  strychnia  solution,  (-05  per  cent.)  Pinching- 
or  touching  curarised  limbs,  which  have  lost  motility,  will 
excite  reflex  motion  in  the  protected  limb.  Curare  does  not 
paralyse  afferent  nerves  or  spinal  centres. 


lO     PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

For  these  two  experiments  the  frog  is  killed  by  de- 
stroying- the  hemispheres:  the  spinal  cord  must  be  left 
intact. 

(c.)  Make  two  preparations  of  muscles  with  nerves  A  and  B. 
Of  A  allow  the  muscle  to  soak  in  curare  dissolved  in  ^  per  cent, 
saline  solution,  keeping  the  nerve  moistened  with  saline.  Of 
B  allow  the  nerve  to  soak  in  curare.  In  about  15  minutes, 
test  muscle  and  nerve  of  both  preparations;  both  muscles  are 
excitable;  the  nerve  of  A  is  inexcitable,  that  of  B  is  excitable. 
Curare  does  not  paralyse  motor  nerve  or  muscle,  but  makes  a 
block  between  nerve  and  muscle. 

24.  Mechanical  Excitation ;  Mechanical  Tetanus.— It  has 
already  been  seen  that  section  or  other  mechanical  injury  is 
an  excitant  of  nerve,  evidenced  by  one  or  more  muscular 
twitches.'"''  Connect  a  Grove  cell  with  the  "Tetanomotor," 
introducing  a  key  into  the  circuit.  The  wire  from  the  zinc 
terminal  of  the  battery  must  be  inserted  in  the  binding  screw 
marked  jE,  that  from  the  platinum  in  Z,  in  Fig.  i.  Adjust  the 
apparatus  so  that  on  closing  the  key  the  ivory  hammer  vibrates 
so  as  to  excite,  without  destroying,  a  nerve  placed  on  the 
ivory  groove.  The  effect  produced  is  identical  with  tetanus  by 
faradisation. 

25.  Experiments  in  which  the  Graphic  Method  is 
used. — For  these  experiments  are  required,  (ij  a  revolving 
cylinder  tightly  covered  with  paper,  and  then  smoked,  of 
which  the  rate  of  rotation  is  known ;  (2)  suitable  means 
for  supporting  a  muscle,  so  that  it  may  act  upon  a  lever 
which  presses  lightly  against  the  moving  surface  of  the 
paper. 

*  The  positive  element  is  a  well  amalgamated  zinc,  immersed  in  ten  per 
cent,  sulphuric  acid  contained  in  a  porous  cell ;  the  negative  element  is  a 
sheet  of  platinum  immersed  in  strong  nitric  acid. 


THE    MYOGRAPH.  II 

By  noting  the  time  required  for  a  given  number  of  revolu- 
tions of  the  cylinder,  and  accurately  measuring  its  circum- 
ference, the  rate  of  motion  of  the  surface  which  is  to  receive 
the  record,  may  be  fairly  determined.  But  for  more  accurate 
purposes,  we  must  make  a  simultaneous  record  of  the  oscilla- 
tions of  a  tuning  fork,  or  of  an  electro-magnetic  time-marker, 
introduced  into  a  circuit  in  which  a  vibrating  reed  acts  as  an 
electro  magnetic  interrupter. 

When  for  the  purposes  of  the  experiment,  it  is  desirable 
that  the  horizontal  motion  of  the  recording  surfaces  should 
be  slow,  i.e.,  less  then  two  inches  per  second,  an  interrupting 
clock  regulated  by  a  pendulum  or  a  metronome,  is  substituted 
for  the  vibrating  reed  in  the  circuit  of  the  time-marker.  This 
is  so  constructed  that  it  makes  and  breaks  the  circuit  at  in- 
tervals of  one  or  more  seconds. 

26.  The  Myograph.— A  simple  and  useful  myograph  is  con- 
structed as  follows : — An  oblong  block  of  wood,  on  which  a 
cork  plate  is  glued,  supports  the  preparation.  At  one  end  of 
the  block  is  a  vertical  stem  or  pillar,  of  which  the  height  and 
distance  from  the  preparation  can  be  varied.  This  pillar  is 
surmounted  by  two  steel  points,  which  face  each  other  at  a 
distance  of  about  three  quarters  of  an  inch.  On  these  the 
axis  of  a  bell-crank  lever  rotates,  of  which  the  horizontal 
arm  is  prolonged  by  a  rod  of  wood  or  thin  vulcanite,  and 
ends  in  a  writing  point.  To  the  vertical  arm,  the  tendon  of 
the  muscle  of  which  it  is  desired  to  record  the  contractions, 
is  attached. 

27.  The  Graphic  Record  or  curve  of  a  Single  Contraction, 
(twitch).  (F.  p.  42,  H.  p.  270).  (a.)  First  arrange  the  re- 
cording apparatus.  For  the  present  purpose  the  cylinder 
must  revolve  about  once  in  two  seconds.  With  the  apparatus 
commonly  used,  a  trigger  key  is  provided,  which  can  be  so 


12      PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

adjusted  that  the  cylinder  opens  it  on  arriving-  at  a  certain 
point  in  its  revolution.  See  that  this  key  is  in  order,  particu- 
larly that  when  it  is  closed  the  contact  is  perfect.  Cover  the 
cylinder  with  g-lazed  paper,  and  smoke  it  over  a  petroleum 
lamp.  Cut  off  the  hind  limbs  of  a  frog-  just  killed  by  pithing", 
and  sever  them  from  each  other.  Place  one  of  them  on  the 
cork  plate,  in  such  a  position  that  the  tibia  is  in  a  line  with 
the  long-  arm  of  the  lever.  Expose  the  tendon  of  the  gastro- 
cnemius and  after  severing-  and  freeing-  it  from  surrounding- 
parts,  tie  to  it  a  bit  of  strong-  ligature  thread  immediately  in 
front  of  the  sesamoid  cartilage.  Then  expose  the  lower  end 
of  the  femur,  and  thrust  through  it  a  strong  needle-point,  to 
which  a  thin  wire  leading  from  one  of  the  binding  screws  at 
the  side  of  the  block  has  been  soldered.  This  serves  to  fix 
the  femoral  attachment  of  the  gastrocnemius.  The  needle  in 
which  the  wire  from  the  other  binding-  screw  ends,  is  to  be 
thrust  through  the  tendon  close  to  the  ligature.  Lastly,  at- 
tach the  thread  to  the  short  vertical  arm  of  the  lever,  bring 
the  myograph  (which  has  up  to  this  time  been  on  the  table), 
into  position,  connect  its  binding  screws  with  the  wires  of  the 
secondary  coil  of  the  induction  apparatus,  which  should  be  at 
a  considerable  distance  from  the  primary.  The  next  step  is 
to  ascertain  to  what  distance  it  is  necessary  to  approximate 
the  secondary  coil,  in  order  to  obtain  a  full  response  to  break 
induction  shocks.  This  having  been  determined,  open  the 
key  in  the  primary  circuit,  bring  the  end  of  the  writing  lever 
into  contact  with  the  smoked  surface,  ascertain  that  the 
trigger  key  is  in  position,  close  it  and  allow  the  cylinder 
to  revolve  slowly  until  the  pin  presses  against  the  trigger. 
Tap  the  tendon  lightly,  and  set  the  clockwork  in  unrestrained 
motion.  As  soon  as  the  fly  has  attained  its  full  expansion, 
momentarily  close  the  key  in  the  primary  circuit. 


INFLUENCE    OF    TEMPERATURE.  1 3 

(i.J  Influence  of  Temperature  on  the  Form  of  the  Curve. 
The  prolong-ation  of  the  single  contraction  produced  by  cold, 
may  be  observed  by  placing"  a  few  bits  of  ice  in  contact  with 
the  skin  by  which  the  muscle  is  covered.  To  study  the  in- 
fluence of  heat,  remove  the  ice,  and  place  on  the  limb  an 
India-rubber  bag  filled  with  warm  water;  you  find  that  the 
contraction  is  shortened.  If  the  water  is  above  40'  C,  the 
muscle  may  become  rigid. 

fc.)  Influence  of  Veratrin.— Inject  a  drop  of  O'l  per  cent, 
solution  of  veratrin  into  the  lymph  sac  of  a  brainless  frog. 
After  twenty  minutes,  destroy  the  spinal  cord  and  inscribe 
one  or  more  muscle  curves,  and  compare  them  with  those 
previously  obtained. 

28.  Superposition  of  two  single  contraction  curves.— 
(F.  p.  47,  H.  p.  274),  For  the  purpose  of  observing  this  it  is 
very  advantageous  to  substitute  the  "pendulum  myograph" 
for  the  revolving  cylinder.  The  pendulum  is  provided  with 
two  trigger  keys  of  the  same  kind  as  that  employed  in  the  last 
experiment,  which  can  be  so  adjusted  that  they  are  opened 
by  the  pendulum  in  its  swing.  According  to  the  distance  at 
which  they  are  placed,  two  circuits  in  which  they  are  severally 
introduced,  are  broken  at  any  desired  time  after  each  other. 
Connect  two  Daniells  with  two  induction  coils.  Arrange  the 
two  trigger  keys  of  the  myograph,  each  in  one  of  the  two 
primary  circuits.  Connect  the  two  secondary  coils  by  one 
terminal  of  each ;  connect  the  remaining  two  poles  with 
electrodes  to  the  muscle,  which  must  be  fixed  on  the  myo- 
graph plate  in  the  same  manner  as  in  (2). 

Make  two  experiments,  one  in  which  the  second  excitation 
follows  the  first  at  an  interval  of  time  shorter  than  one- 
hundredth  of  a  second,  the  other  in  which  the  interval  is  pro- 
longed to  five-hundredths.  In  the  second  there  is  accumu- 
lation of  effect,  but  not  in  the  first. 


14  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

29.  Composition  of  Tetanus. — Use  a  revolving  cylinder 
which  rotates  once  in  about  ten  seconds.  The  arrangement 
of  the  circuit  must  be  as  in  4.  A  key  is  required  in  the  se- 
condary circuit  (See  13)  and  an  interrupter  of  the  following 
kind  into  the  primary,  (a)  Fix  one  end  of  a  steel  spring  con- 
nected with  one  wire  in  a  clamp  so  that  when  it  is  made  to 
oscillate  the  other  end  dips  by  its  bent  down  point  into  and 
out  of  mercury  contained  in  a  cup  to  which  the  other  wire  is 
attached.  Set  the  secondary  coil  at  such  a  distance  that  the 
break  shock  is  alone  effectual.  Make  several  experiments, 
first  with  the  spring  of  such  length  that  the  interruptions 
occur  three  or  four  times  in  a  second  ;  a  second  with  seven 
or  eight  interruptions  per  second,  and  so  on  until  the  spasms 
which  were  in  the  first  experiment  distinct  become  completely 
fused,  (b)  Substitute  for  the  spring  and  mercury  pool  an 
interrupter  which  can  be  rapidly  worked  by  the  finger  used 
as  in  striking  a  pianoforte  key.  Strike  as  frequently  and  reg- 
ularly as  possible — say  seven  times  per  second.  If  the  muscle 
is  fresh  fusion  will  be  incomplete.  Paradise  it  once  or  several 
times  and  repeat  the  observation. 

30.  Influence  of  fatigue.  (F  p.  88).  (a)  Arrange  an  ex- 
periment exactly  as  in  27,  but  instead  of  closing  the  pri- 
mary circuit  for  a  moment  only  (see  last  line  of  paragraph) 
allow  it  to  remain  closed.  A  series  of  contractions  are  re- 
corded. The  height  of  the  contractions  at  first  increases, 
afterwards  diminishes;  the  interval  of  time  between  the 
moment  of  excitation  and  that  at  which  the  lever  attains  its 
greatest  height  gradually  increases.  For  the  sake  of  distinct- 
ness record  only  one  in  ten  of  the  curves,  for  which  purpose 
the  adjusting  screw  must  be  used  to  withdraw  the  lever  from 
the  paper  during  the  intervening  contractions,  (b)  Repeat 
the  same  experiment  using  a  recording  surface  of  which  the 


ELECTROTONUS.  15 

rate  of  motion  is  not  more  than  a  miilim.  per  second.  In  this 
case  each  contraction  is  recorded.  It  is  seen  that  during"  the 
observations  the  rate  of  diminution  of  effect  is  uniform,  so 
that  the  line  connecting"  the  apices  of  the  contraction  curve  is 
straight. 

31.  Experiments  relating  to  Electrotonus.  (F.  p.  40,  H. 
P-  337)-  I"  these  experiments  as  in  5  b.  the  slowly  revolving 
cylinder  must  be  used.  The  muscle  and  nerve  must  be  pre- 
pared as  follows: — Strip  off  the  skin,  cut  across  the  trunk 
half  way  down  the  back.  Remove  the  viscera  and  the  wall  of 
the  visceral  cavity.  Lay  the  preparation  on  the  cork  plate, 
ventral  surface  downwards.  Expose  the  sciatic  nerve  in  the 
hollow  of  the  knee.  Thrust  one  blade  of  the  scissors  between 
nerve  and  femur  with  its  back  to  the  nerve  and  divide  the 
femur  about  a  third  of  an  inch  from  the  knee.  Free  the  nerve 
from  surrounding  parts  following  it  to  its  origin,  carefully 
severing  its  muscular  branches.  Cut  away  everything  ex- 
cepting the  remainder  of  the  vertical  column  to  which  the 
nerve  is  still  attached,  and  lastly  fix  the  cut-off  end  of  the 
femur  in  the  clamp  of  the  myograph.  In  all  cases  in  which 
as  in  the  study  of  electrotonus,  the  nerve  must  be  separated 
from  the  surrounding  parts,  it  is  necessary  either  to  support 
and  enclose  it  during  the  period  of  observation  in  a  covered 
trough,  or  to  place  the  myograph  and  preparation  in  a  moist 
chamber,  of  such  construction  that  the  lever  on  which  the 
muscle  acts  is  not  enclosed. 

The  muscle  chamber  (F.  p.  72)  contains  two  pairs  of  non- 
polarisable  electrodes,  the  wires  from  which  are  connected  with 
binding  screws  outside.  To  these  the  following  form  is  given 
for  economy  of  space.  Each  wire  is  soldered  to  a  zinc  rod,  one 
end  of  which  is  carefully  polished  and  amalgamated.  Over 
the  amalgamated  end  is  drawn  a  sheath  (like  the  finger  of  a 


l6  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

glove)  of  wash  leather  steeped  in  zinc  sulphate  solution.  This 
is  further  enclosed  in  a  wider  sheath  steeped  in  o"6  per  cent, 
solution  of  chloride  of  sodium,  the  outside  of  which  is  smeared 
with  kaolin  paste  made  with  the  same  solution.  The  nerve 
is  supported  by  a  vulcanite  trough  which  is  supported  hori- 
zontally by  the  pillar  of  the  myograph  in  such  a  position 
as  to  receive  the  whole  of  the  nerve  conveniently  when 
the  preparation  is  in  position.  The  sides  of  the  trough 
have  notches  at  intervals,  through  which  thick  ligature 
threads  pass  underneath  the  nerve;  the  opposite  ends  of 
each  thread  are  tied  together  below.  Before  putting  the 
threads  in  their  places  they  are  well  soaked  in  salt  solution 
and  smeared  with  soft  kaolin  paste.  The  ends  of  the  threads 
serve  to  bring  them  into  connection  with  the  sheaths  of  the 
zinc  rods,  which  are  supported  by  their  wires  in  a  suitable 
position  for  the  purpose.  Non-polarisable  electrodes  of  this 
form  can  only  be  used  in  the  moist  chamber. 

Use  two  Daniells  for  the  "polarising"  current.  Connect 
them  with  the  middle  binding  screws  of  a  Pohl's  reverser, 
from  which  two  other  wires  proceed  to  the  end  blocks  of  the 
Rheochord  (I.  i6).  Connect  block  A  of  the  Rheochord  with 
one  of  the  electrodes//  and  the  slider  with  the  other.  Con- 
nect the  secondary  coil  of  the  induction  apparatus  with  the 
electrodes  xx .  Either  single  induction  shocks  or  faradisation 
may  be  used  to  test  the  excitability  of  the  nerve.  If  the  latter, 
arrange  the  induction  apparatus  as  in  I.  8. 

(a)  Find  the  minimum  distance  of  coil  at  which  contrac- 
tion occurs  in  the  absence  of  the  polarising  current,  and  then 
remove  the  coil  just  beyond  that  minimum.  Make  the  polar- 
ising current  descending.  If  you  are  examining  by  single 
shocks,  you  see  at  each  excitation  strong  single  twitches ;  if 
by  faradisation  you  see  that  the  muscle  enters  into  tetanus. 


LAW    OF    CONTRACTION.  1 7 

It  has  thus  been  shown  that  the  excitability  is  increased  in  the 
vicinity  of  the  cathode  during  the  passage  of  the  continuous 
current.  (b)  Push  the  coil  a  little  within  the  minimum,  so 
as  to  obtain  evident  contractions,  or  tetanus,  according  to 
your  arrangement.  Make  the  polarising  current  ascending. 
If  you  continue  to  test  by  single  shocks,  you  find  that  they  no 
longer  cause  contraction;  if  by  faradisation,  that  the  tetanus 
is  cut  short.  The  excitability  is  therefore  diminished  in  the 
vicinity  of  the  anode  during  the  passage  of  the  continuous 
current,  (c)  Employ  single  shocks  to  examine  the  after 
effects,  viz.,  the  state  of  excitability  after  the  passage  of  the 
continuous  current.  You  find  that  the  excitability  is  increased 
after  the  passage  of  the  continuous  current  in  either  direction, 
32.  Demonstration  of  the  Law  of  Contraction.  (F.  p.  75, 
H.  p.  338).  For  this  purpose  the  arrangements  required  are 
the  same  as  for  experiments  on  electrotonus,  with  the  excep- 
tion that  the  induction  apparatus,  and  the  battery  and  elec- 
trodes connected  with  it,  are  not  wanted.  The  key  in  the 
primary  circuit  must  be  a  mercurial  one,  and  in  perfect  order. 
Having  completed  the  connections,  close  and  open  this  key  at 
intervals  of  two  seconds,  so  as  to  make  and  break  the  primary 
circuit,  gradually  increasing  the  distance  of  the  slider  of  the 
rheochord  from  the  block  until  the  muscle  begins  to  contract 
at  make.  This  effect  is  usually  observed  sooner,  i.e.,  with  a 
weaker  current  when  its  direction  is  from  the  muscle.  At 
once  shift  the  slider  to  the  second  length.  The  muscle  will 
probably  respond  to  both  make  and  break,  whether  it  is 
directed  from  or  towards  the  muscle.  Now  substitute  for  the 
two  Daniells  half  a  dozen  Groves,  or  Lechanches,  and  dis- 
pense with  the  rheochord.  Under  these  conditions  contraction 
occurs  at  make  only  when  the  current  is  towards  the  muscle, 
at  break  only  when  it  is  towards  the  spinal  cord. 

c 


l8  PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

33.  Bitter's  Tetanus.  (F.  p.  76,  H.  p.  339).  Conduct  a 
continuous  current  of  such  streng"th  as  to  g-ive  the  third  stage, 
throug-h  a  nerve  for  a  short  time,  the  direction  of  which 
should  be  towards  the  spinal  cord.  On  breaking  the  current, 
the  muscle  enters  into  tetanus,  which  can  be  instantly  ar- 
rested by  again  closing  the  current,  or  by  cutting  the  nerve 
near  the  muscle,  but  is  not  aboHshed  by  cutting  the  nerve 
midway  between  the  electrodes.  It  is  sometimes  possible  to 
observe  the  same  effect  on  opening  a  current  directed  towards 
the  muscle.  If  so,  it  can  be  abolished  by  severing  the  nerves 
between  the  electrodes.  It  is  therefore  dependent  on  condi- 
tions which  have  their  seat  at  the  anode. 

34.  Experiments  to  Demonstrate  the  Seat  of  the  Physio- 
logical Influence  of  Fatigue.— Arrange  two  nerve -muscle 
preparations,  A  and  B,  loaded  equally  with  50  grms.  each, 
with  the  nerves  on  the  same  pair  of  electrodes,  connected 
with  the  secondary  coil.  Below  this  point,  on  the  nerve  B, 
apply  the  electrodes  (unpolarisable)  of  a  single  Daniell,  pre- 
ferably so  that  the  current  is  descending.  Faradise,  and  at 
the  same  time  make  the  continuous  current ;  the  muscle  A, 
will  enter  into  tetanus,  B  will  remain  quiescent,  the  stimulus 
being  blocked  by  the  electrotonic  zone.  Continue  faradisa- 
tion until  the  tetanus  of  A  has  quite  subsided,  then  break  the 
constant  current ;  B  will  forthwith  enter  into  tetanus.  Both 
nerves  have  been  equally  stimulated,  and  are,  therefore, 
equally  fatigued;  the  tetanus  of  B  shows  that  the  excit- 
ability of  its  nerve  was  not  exhausted,  and  consequently  that 
the  apparent  exhaustion  of  A  was  not  nervous. 

Connect  a  nerve-muscle  preparation  with  two  pairs  of 
electrodes,  one  pair  to  the  nerve,  the  other  to  the  muscle. 
Connect  their  wires  to  the  two  sides  of  a  switch,  so  that  you 
can  rapidly  transfer  the  current  from  one  pair  to  the  other. 


PERIOD    OF    LATENT    STIMULATION.  IQ 

Paradise  the  nerve  until  tetanus  has  quite  subsided,  then 
transfer  the  current  to  the  muscle.  The  apparently  ex- 
hausted muscle  enters  into  tetanus.  For  both  experiments 
the  slowly  revolving-  cylinder  should  be  used. 

35.  Measurement  of  the  Period  of  Latent  Stimulation  by 
the  Pendulum  Myograph.  (F.  p.  43,  H.  p.  271).  Prepara- 
tion of  the  apparatus.  Cover  the  glass  plate  smoothly  with 
paper,  smoke  its  surface  as  before,  and  fix  it  to  the  pen- 
dulum. Arrange  the  "detent"  and  the  "catch"  so  that 
the  pendulum,  when  detached  from  the  former,  just  catches 
on  the  latter.  Test  the  instrument  by  taking  tracings  with  a 
tuning-fork,  vibrating  lOO  times  a  second,  on  the  smoked 
paper,  when  the  pendulum  is  moving  at  several  different 
velocities  (the  velocity  varying  with  the  positions  of  the  de- 
tent and  catch).  Arrange  the  electrical  apparatus  for  single 
shocks,  as  in  4,  including  in  the  primary  circuit  one  of  the 
keys  of  the  myograph.  Prepare  the  gastrocnemius  as  in  27. 
Great  care  must  be  taken  in  fixing  the  femur  immovably 
to  the  cork  plate,  in  attaching-  the  ligature  (for  which  thin 
wire  may  be  advantageously  substituted)  to  the  tendon 
and  lever.  See  also  that  no  part  of  the  apparatus  touches 
the  surface  of  the  glass  plate,  as  the  pendulum  swings,  except- 
ing- the  writing  point,  and  that  the  pressure  of  the  point  on 
the  plate  is  slightly  greater  towards  the  end  than  at  the 
beginning  of  the  swing-.  Bring  back  the  pendulum  to  its 
place  and  see  that  everything-  is  in  order — the  keys  closed, 
the  lever  in  its  position,  the  electrodes  under  the  nerve,  etc. 
On  liberating-  the  pendulum,  a  muscle  curve  is  inscribed  on 
the  smoked  surface.  Withdraw  the  lever  from  its  writing- 
position,  bring-  the  pendulum  back  past  the  key,  close  the 
latter,  keeping  it  closed  by  firm  pressure  of  the  finger,  allow 
the  pendulum  to  rest  against  it,  bring  the  lever  into  the  writ- 

c  2 


20     PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

ing-  position,  and  make  a  mark  on  the  surface,  which  indicates 
the  moment  of  excitation.  Take  three  or  four  similar  curves, 
depressing-  the  table  an  equal  distance  after  each  observation 
(I  or  ^  turn)  by  the  handle.  Remove  the  muscle  lever,  and 
take  a  tracing  v^ith  a  tuning--fork,  vibrating-  lOO  times  a 
second,  carefully  arranging  the  style  of  the  fork  in  the  posi- 
tion previously  occupied  by  the  writing  end  of  the  muscle 
lever.  Remove  the  paper,  varnish  and  measure  the  tracings. 
From  the  mean  result  of  the  measurements,  the  latent  stimu- 
lation may  be  computed. 

36.  Rate  of  Propagation  in  Nerve.  (F.  p.  45,  H.  p.  345). 
(a J  In  the  frog. — The  arrangements  are  the  same  as  for  the  last 
experiment.  The  nerve  must  be  placed  in  a  vulcanite  trough 
similar  to  that  employed  in  31,  with  the  exception  that  in- 
stead of  threads,  two  pairs  of  wires  cross  the  floor  of  the 
trough  at  a  distance  of  about  an  inch  from  each  other.  The 
nerve  must  be  prepared  with  great  care,  as  in  I.,  3,  and  must 
be  in  contact  with  both  pairs  of  wires.  Connect  each  couple 
of  wires  with  the  side  binding  screws  of  a  Pohl's  reverser 
from  which  the  cross  wires  have  been  removed,  and  the  wires 
of  the  secondary  coil  to  the  middle  screws,  so  that  by  turning 
over  the  bridge,  the  near  and  the  distant  portion  of  the  nerve 
can  be  excited  alternately.  Cover  the  trough  with  a  flap  of 
muscle,  taking  care  that  the  flap  does  not  touch  the  nerve. 
Make  a  series  of  observations,  throwing  over  the  bridge 
between  each.  Then  take  a  tuning-fork  tracing,  varnish, 
measure  the  length  of  nerve  between  the  two  contacts,  and 
calculate  therefrom  the  rate  of  propagation,  fd)  The  pen- 
dulum myog-raph  may  also  be  used  to  measure  the  rate  of 
propagation  in  human  motor  nerve,  the  observer  experiment- 
ing on  himself.  Arrange  a  Marey's  tympanum,  so  that  its 
lever  may  write  on  the  glass  plate.     Connect  the  tympanum 


ELASTIC    PROPERTIES    OF    MUSCLE.  21 

by  an  elastic  tube  in  which  there  must  be  a  small  aperture 
for  the  escape  of  air,  with  a  pair  of  toy  bellows  held  between 
the  thumb  and  finger  of  the  left  hand.  Arrang-e  the  primary 
circuit  as  before.  Connect  one  electrode  of  large  area  from 
the  secondary  coil  with  any  part  of  the  body.  Apply  a  small 
metal  disc  covered  with  wash  leather  steeped  in  strong-  solu- 
tion of  salt  to  the  skin,  first  at  the  bend  of  the  elbow,  and  for 
a  second  observation,  above  the  clavicle,  arranging  the  lever 
of  the  tympanum  so  that  the  two  curves  shall  be  close  to- 
gether. Then  make  a  scries  of  similar  observations  in  pairs, 
taking  care  to  allow  the  pendulum  to  draw  a  base  line  to  each 
curve.  Measure  on  the  base  lino  the  distance  between  the 
curves  of  each  pair,  rejecting  all  records  in  which  the  two  are 
not  of  the  same  amplitude.  The  results  obtained  by  this  rough 
method  are  surprisingly  constant.  They  show  that  the  rate 
of  propagation  in  man  much  exceeds  that  observed  in  the 
frog. 

37.  The  Elastic  Properties  of  Muscle.— (a J  For  experi- 
ments on  this  subject,  use  the  slowly  revolving  cylinder,  and 
a  counterpoised  writing  lever,  two  or  three  feet  in  length. 
Arrange  the  gastrocnemius  as  in  31,  substituting  a  scale 
pan  for  the  weight.  Attach  the  tendon  and  scale  pan  to  the 
lever  at  as  short  a  distance  as  possible  from  the  writing 
point.  Prepare  four  equal  weights  of  from  20  to  25  grammes 
each,  and  cautiously  place  them  in  succession  on  the  scale 
pan  while  the  cylinder  is  revolving.  Observe  that  the  exten- 
sion is  greater  for  the  first  weight,  less  for  the  next,  and  so 
on ;  and  that  the  increase  of  length  after  each  addition  of 
weight  is  gradual.  On  removing  the  weight,  the  muscle 
resumes  nearly  its  original  length,  which,  however,  it  never 
completely  attains,  although  it  continues  to  shorten  for  some 
time  after  it  ceases  to  be  acted  upon  by  the  weight. 


22  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

(b)  To  compare  the  extensibility  of  tlie  muscle  during-  rest 
and  action,  load  it  successively  with  two  weights,  say  of  50 
grammes  and  10  grammes.  Determine  the  height  to  which 
the  point  of  the  lever  rises  in  tetanus  with  the  two  weights  in 
succession,  and  compare  the  difference  between  the  two,  with 
the  extension  of  the  untetanised  muscle,  when  successively 
loaded  with  the  same  weights. 


II. — The  Frog  Heart. 

1.  Rhytlimical  Motions.— In  a  curarized  preparation  of 
which  the  hemispheres  have  been  destroyed,  expose  the  ster- 
num, and  cut  across  the  episternal  cartilage.  Then  sever  the 
sternum  from  its  connections  by  a  cut  on  either  side,  and  turn 
it  down  over  the  belly.  The  heart  is  seen  still  covered  by  the 
pericardium.  Note  the  condition  of  each  of  its  cavities,  and 
the  mode  of  its  rhythmical  action. 

2.  The  Inhibitory  Centre.  (F.  p.  170).  For  the  purpose 
of  observing  the  effect  of  passing  series  of  induction  shocks 
through  the  inhibitory  centre  of  the  heart,  a  fine  ligature  is 
attached  to  the  fraenum  (the  thread-like  ligament  which 
stretches  from  the  dorsal  aspect  of  the  ventricle  towards 
the  lower  part  of  the  pericardium).  By  means  of  the  liga- 
ture, the  heart  is  raised  out  of  its  place  and  turned  upwards. 
The  inhibitory  centre  is  recognized  by  the  whitish,  crescent- 
shaped  line,  which  marks  the  junction  of  the  wall  of  the  sinus 
with  that  of  the  right  auricle.  Paradise  this  spot  for  a  second, 
or  less,  placing  the  points  of  the  electrodes  on  the  line,  a 
couple  of  millims.  distant  from  each  other.  Observe  the 
mode  and  order  in  which  the  cavities  of  the  heart  resume 
thpir  rhvthmical  action. 


THE    FROG    HEART.  23 

3.  Destroy  the  spinal  cord  by  pithing,  and  observe  the 
changes  thereby  produced  in  the  state  of  the  circulation,  and 
particularly  in  the  mode  of  action  of  the  heart. 

4.  The  Cardiac  Vagus  of  the  Frog.— (a)  Preliminary  Dis- 
section.— Expose  the  trunk  of  the  vagus  nerve  as  it  escapes 
from  the  cranium  as  follows : — Remove  the  integument  so  as 
to  bring  into  view  the  muscles  of  the  back  of  the  neck  on  one 
side,  avoiding  injury  to  the  cutaneous  vessels.  Then  expose 
the  scapula,  and  sever  with  the  scissors  the  cartilaginous 
from  the  bony  scapula;  remove  the  former,  dividing  the 
muscles  attached  to  it,  then  expose  the  sterno-mastoid  muscle 
which  connects  the  outer  part  of  the  petrous  bone  and  the 
posterior  border  of  the  cartilaginous  ring  of  the  membrana 
tympani  with  the  concave  anterior  border  of  the  scapula. 
Remove  or  draw  aside  the  sterno-mastoid  so  as  to  expose  the 
slender  muscles  (petrohyoidei)  which  run  from  the  petrous 
bone  to  the  posterior  horn  of  the  hyoid  bone,  embracing  the 
cavity  of  the  pharynx.  Parallel  with  these  muscles,  and  in 
close  relation  with  them,  are  seen  the  carotid  artery  and 
several  nerves,  of  which  the  two  nearest  the  cranium  are  the 
glosso-pharyngeal,  and  the  vagus. 

(d)  Expose  the  vagus  in  a  pithed  preparation.  Expose  the 
heart,  as  in  1,  and  introduce  a  small  test  tube  into  the 
guUett.  Fix  the  preparation  in  such  a  position  on  a  cork, 
that  the  electrodes  can  be  conveniently  applied  to  the  nerve, 
at  the  same  time  that  the  motion  of  the  heart  can  be  ob- 
served. 

5.  The  Stannius'  Heart.—Prepare  a  frog  heart  with  frae- 
num  ligature  as  before.  Then  pass  a  thick  ligature  under  the 
bifurcation  of  the  aorta  between  it  and  the  venae  cavae  superi- 
ores.  Then,  seizing  the  fraenum  ligature  with  the  forceps, 
turn   the   heart  up.      Carefully  observe   the    position    of   the 


24  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

"  crescent,"  and  loop  the  ends  of  the  ligature  so  that  when  it 
is  tightened  it  may  embrace  the  crescent.  On  tightening,  the 
heart  will  stop  in  diastole. 

In  the  heart  so  prepared,  sever  the  ligatured  parts  from  the 
rest  of  the  preparation  with  sharp  scissors.  The  auricles  and 
ventricles  resume  their  normal  rhythmical  action. 

Cut  off  in  a  preparation  which  has  been  so  treated,  the  re- 
mainder of  the  auricles  and  the  bulb,  leaving  the  ventricle 
and  auriculo- ventricular  septum.  The  heart  continues  to 
beat  normally,  or,  if  the  beats  cease,  they  are  renewed  by  a 
pinch,  by  an  induction  shock,  or  by  bringing  a  hot  wire  into 
the  neighbourhood  of  the  cut  surface. 

6.  Localization  of  the  Motor  Centres.  -In  one  of  two  such 
preparations  (called  ventricle  preparations)  which  beat  rhyth- 
mically, cut  off  the  whole  of  the  auriculo-ventricular  furrow 
with  sharp  scissors.  The  preparation  so  obtained  (the  ven- 
tricle apex)  does  not  contract  spontaneously,  but  responds  to  a 
single  excitation,  whether  mechanical  or  electrical,  by  a  single 
contraction,  the  duration  of  which  is  dependent  on  the  tempera- 
ture. In  the  other  preparation,  divide  the  ventricle  by  two 
parallel  cuts  into  a  middle  and  two  lateral  thirds.  The  middle 
third  includes  the  ventricular  border  of  the  inter-auricular 
septum,  the  right  lateral  third  contains  the  root  of  the  bulb. 
The  middle  third  beats  rhythmically,  the  lateral  thirds  re- 
spond to  excitations  by  single  contractions,  but  do  not  beat  of 
themselves. 

7.  Action  of  Muscarin  and  Atropin.— In  an  entire  heart 
(a  heart  removed  by  severing  the  vessels,  for  which  purpose 
the  organ  should  be  lifted  out  of  the  pericardium  by  a  liga- 
ture tied  to  the  frsenum),  stop  rhythmical  action  by  applying 
to  it  a  drop  of  serum  containing  a  trace  of  muscarin.  Ob- 
serve the  relaxed  and  motionless  condition  of  the  ventricle. 


THE    FROG    HEART.  2$ 

After  a  few  minutes,  apply  (in  serum)  a  drop  of  0*2  per 
cent,  solution  of  atropin.  Observe  the  gradual  restoration 
of  rhythmical  action  in  the  atropinized  heart.  Observe  that 
faradisation  of  the  Inhibitory  centre  is  without  effect. 

8.  Action  of  the  Constant  Current  on  the  Contractile 
Substance  of  the  Heart.— For  this  purpose  prepare  elec- 
trodes as  directed  in  i.  Fix  a  cork  vertically  on  a  sheet 
of  lead  about  an  inch  and  a  half  square ;  cover  the  top 
of  the  cork  with  wax  mass,  the  upper  surface  of  which 
should  be  somewhat  concave.  Place  the  support  on  a  sheet 
of  wet  filtering-  paper  and  cover  it  with  a  beaker.  Attach  a 
fine  ligature  to  the  fraenum,  and  remove  the  heart  after  sever- 
ing the  principal  vessels.  Collect  some  blood  and  dilute  it 
with  as  much  as  0*75  per  cent,  salt  solution,  and  place  a  few 
drops  of  it  on  the  wax  surface. 

Make  a  "ventricle-apex  preparation,"  as  directed  in  6. 
Having  ascertained  that  it  does  not  beat  rhythmically  of  itself, 
fix  it  in  its  place  by  the  aid  of  fine  glass  pins  and  replace  the 
beaker. 

Prepare  and  arrange  two  Grove's  cells  in  circuit,  interpose 
a  key  and  a  pair  of  electrodes.  Fix  the  electrodes,  so  that 
their  points  are  in  contact  with  the  apex  and  base  respectively 
of  the  preparation.  The  passage  through  the  ventricle  apex 
of  a  voltaic  current  in  the  direction  of  its  axis,  produces  rhyth- 
mical action,  which  lasts  as  long  as  the  current  passes. 

9.  Study  of  the  Ventricular  Systole  by  the  Graphic 
Method.— Prepare  a  writing  lever  consisting  of  a  glass  rod 
about  -^\^  inch  in  thickness,  and  five  inches  long,  having  at 
one  end  a  knob  of  glass,  and  at  the  other  a  writing  point. 
This  is  thrust  through  a  square  bit  of  cork,  which  is  then 
pushed  up  to  the  knob.  A  fine  steel  needle  passes  through 
the  cork  at  right  angles  to  the  rod.      The  rod  also  bears. 


26      PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

close  to  the  needle,  a  vertical  arm  of  cork,  by  means  of  which 
it  rests  on  the  ventricle.  The  preparation  lies  on  a  metal 
plate,  which  forms  the  upper  end  of  a  cylindrical  brass  box, 
through  which  water,  at  any  desired  temperature,  can  be 
passed.  This  plate  is  furnished  with  bearings  in  which  the 
steel  axis  of  the  lever  works.  The  metal  box  is  fixed  to  one 
of  the  adjustable  supports  of  the  recording  apparatus. 

(a)  The  rhythmically  contracting  heart. 

Expose  the  heart  as  before.  Raise  it  from  the  pericardium 
by  a  ligature  attached  to  the  severed  fraenum,  and  cut  through 
the  vessels.  Place  the  heart  on  a  plate,  adding  a  few  drops 
of  dilute  serum,  and  arrange  the  lever  so  that  the  cork  arm 
rests  on  the  ventricle,  and  the  writing  end  inscribes  its  move- 
ments on  the  blackened  surface  of  the  cylinder.  The  rate  of 
motion  should  be  about  20  inches  per  minute. 

Allow  water  at  12°  C.  to  pass  through  the  cylindrical  box 
and  record  the  rhythmical  contractions  of  the  ventricle.  Re- 
peat the  experiment,  substituting  water  at  17°  and  at  22°,  and 
compare  the  tracings.  • 

(b)  The  curve  of  a  single  ventricular  contraction. 
Prepare  finely  pointed  electrodes,  as  in  I.  i,  arranging  for 

single  induction  shocks.  Fix  the  electrodes  to  an'  adjustable 
support,  so  that  they  can  be  brought  with  precision  into  con- 
tact with  the  preparation.  Prepare  a  Stannius'  heart  and 
arrange  it  for  recording  as  in  a.  Adjust  the  electrodes, 
taking  care  not  to  interfere  with  the  lever.  Place  the  secon- 
dary coil  at  about  10  centimeters  distance  from  the  primary, 
or  nearer,  if  on  trial  it  is  found  necessary  to  do  so.  Then 
bring  the  point  of  the  lever  into  contact  with  the  blackened 
paper,  so  as  to  write  a  base  line  or  abscissa,  and  open  the 
key.  The  rate  of  motion  of  the  recording  surface  should  be 
about  2\  inches  per  second. 


SPINAL    AND    OTHER    REFLEX    CENTRES.  ^'] 

In  order  to  obtain  series  of  tracings  which  can  be  con- 
veniently compared,  introduce  into  the  primary  circuit  the 
self-acting"  key  described  in  I.,  28.  In  this  way  a  number  of 
curves  may  bedrawn  on  the  same  abscissa,  or  on  parallel 
abscissae  at  convenient  distances  from  each  other.  Having 
practised  one  or  other  of  these  methods,  proceed  to  make  the 
following  observations : — 

a.  When  a  succession  of  ventricular  curves  are  drawn  at 
temperatures  varying  from  12°  to  18°,  C,  it  is  found  that  the 
duration  of  the  systole  is  increased  by  about  o"'i  for  every 
degree  of  temperature. 

/3,  When  the  ventricle  is  excited  by  single  induction  shocks, 
following  each  other  at  about  10"  intervals,  each  curve  is 
observed  to  exceed  its  predecessor  in  amplitude,  the  aug- 
ments gradually  diminishing  from  the  beginning  to  the  end 
of  the  series. 

y.  In  the  muscular  tissue  of  the  heart,  the  period  of  latent 
stimulation  is  much  longer  than  in  voluntary  muscle.  Its 
duration  is  about  o"*i5.  To  measure  it,  a  vertical  line  must 
be  drawn  on  the  recording  surface,  indicating  the  position  of 
the  writing  point  at  the  moment  that  the  trigger  of  the  cylin- 
der comes  into  contact  with  the  lever  of  the  self-acting  key. 
{See  I.,  28). 


III. — Functions  of  the  Spinal  and  other  Reflex  Centres 
OF  THE  Frog. 

!•  (F-  537»  H-  479)-  The  preparation  to  be  used  in  the 
following  experiments  is  obtained  by  severing  the  spinal  cord 
immediately  behind  the  medulla  oblongata,  and  introducing, 
by  the  opening  made  for  this  purpose,  a  wooden  plug  into 
the  cranial  cavity,  so  as  to  destroy  its  contents.     This  having 


28      PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

been  done,  it  is  placed  on  a  sheet  of  moist  filter- paper,  rest- 
ing- on  its  ventral  surface  with  the  hind  limbs  extended,  and 
covered  with  a  bell  jar.  For  a  time  it  remains  motionless, 
but  eventually  assumes  a  position  which  differs  but  little  from 
that  of  a  living-  frog.     Observe  the  differences. 

2.  Prepare  half-a-dozen  pieces  of  filter-paper,  each  an 
eighth  of  an  inch  square,  and  some  strong  acetic  acid. 
Turn  the  preparation  over,  and  after  observing  that  the 
natural  position  is  not  resumed,  apply  one  of  the  squares, 
after  moistening  it  with  acetic  acid  and  drawing  off  excess 
by  touching  with  dry  filter  paper,  to  the  inside  of  the  right 
thigh,  and  observe  the  result.  Repeat  the  experiment,  hold- 
ing the  right  foot.  Next,  attach  the  preparation  to  a  suitable 
holder  in  such  a  way  that  the  trunk  may  be  steadily  supported 
and  the  limbs  may  hang  freely,  and  apply  the  squares  in  suc- 
cession to  different  parts  of  the  surface,  as  e.g.,  to  the  skin  on 
either  side  of  the  tendo  Achillis,  or  to  either  flank.  Observe 
in  each  case  that  the  muscular  response  which  results  from  ex- 
citation of  the  same  part  of  the  surface  of  the  body  is  always 
the  same. 

3.  Arrange  a  second  preparation  as  last  described,  using  a 
holder  so  constructed  that  the  limbs  may  be  suspended  at  any 
desired  height  above  the  table.  Prepare  several  beakers  of 
water  acidulated  respectively  with  i,  2,  3,  4,  and  5  per  thou- 
sand of  sulphuric  acid,  and  place  some  of  each  mixture  in  a 
saucer.  Beginning  with  the  weakest  of  the  acid  liquids,  bring 
down  the  preparation  with  the  rack  and  pinion,  until  the  tip 
of  the  longest  toe  is  immersed.  Repeat  the  experiment  at 
intervals  of  three  minutes  with  the  stronger  liquids,  in  order, 
carefully  washing  the  foot  after  each  excitation,  by  dipping  it 
into  a  beaker  of  water.  Measure  the  time  which  intervenes 
between  the  beginning  of  the  excitation  and  the  muscular  re- 
sponse in  each  case,  with  the  aid  of  a  metronome. 


SENSATION  AND  PERCEPTION.  29 

4.  Observe  carefully  the  attitude  of  a  brainless  frog  when 
left  to  itself,  and  its  behaviour  when  placed  on  its  back,  on 
an  inclined  surface,  or  in  water,  as  well  as  when  excited  by 
cutaneous  stimuli,  comparing  the  phenomena  observed  with 
those  which  exhibit  themselves  in  the  spinal  cord  preparation. 

5.  Proceed  as  in  i,  substituting  a  preparation  in  which, 
after  destruction  of  the  brain,  a  couple  of  drops  of  a  0"i  per 
cent,  solution  of  sulphate  of  strychnia  have  been  injected  un- 
der the  skin  of  the  back.  Observe  that  instead  of  co-ordinate 
muscular  responses,  cutaneous  excitation  produces,  under  the 
influence  of  strychnia,  paroxysms  of  convulsion,  in  which  the 
body  and  limbs  assume  a  characteristic  attitude. 

IV. — Sensation  and  Perception. 

I.  Time  Occupied  in  the  Simplest  Mental  Processes. 
(F.  594,  H.  511J.  To  measure  the  time  required  for  re- 
sponding to  a  signal  (reaction  time  or  personal  time),  the 
simplest  plan  is  to  arrange  a  battery  circuit  in  such  a 
way  that  it  is  closed  by  the  same  act  by  which  the  ob- 
server makes  the  signal,  and  that  it  is  opened  by  the  re- 
sponse of  the  observed  person.  Whatever  be  the  nature  of 
the  signal,  the  requirements  are: — (1)  Two  Grove's  cells 
arranged  in  circuit;  (2)  a  break  key,  (a  lever  resembling 
in  shape  a  pianoforte  key,  which,  when  touched,  breaks  a 
mercurial  contact);  (3)  a  du  Bois'  key;  (4)  an  electro- 
magnet with  a  light  lever  attached  to  its  armature;  (5)  a 
chronograph ;  (6)  a  recording  surface,  of  which  the  rate  of 
motion  is  not  less  than  i  foot  per  second.  The  battery,  two 
keys,  electro-magnet,  and  chronograph,  are  arranged  in  cir- 
cuit, and  in  such  positions  that  the  electro-magnet  lever  may 
be  in   the  neighbourhood  of  the  observed  person,   and   the 


30  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

du  Bois'  key,  cylinder,  and  chronograph,  in  reach  of  the 
observer.  On  closing-  the  circuit,  the  lever  is  drawn  towards 
the  magnet  and  gives  the  signal.  The  signal  may  be  an  in- 
duction shock  through  the  tip  of  the  tongue,  (in  which  case 
an  induction  coil  must  be  in  circuit  in  addition  to  the  instru- 
ments above  mentioned),  a  touch  on  the  hand  given  by  the 
lever,  a  sound,  or  a  visible  signal,  such  as  a  white  disk,  letter, 
or  number,  suddenly  brought  into  view^ 

2.  Tactile  and  Muscular  Sensation,  (F.  529,  530,  H. 
463-469).  In  all  the  following  experiments  two  persons  must 
take  part,  one  of  whom  must  vary  the  conditions  without 
the  knowledge  of  the  other,  and  note  the  results.  In  the 
experiments  relating  to  the  sensations  of  pressure,  locality, 
and  muscular  exertion,  the  observed  person  must  have  his 
eyes  shut. 

The  appreciation  of  Temperature  must  be  tested  by  im- 
mersing the  same  surface  successively  in  water  of  slightly 
different  temperatures.  The  smallest  differences  can  be 
detected  when  the  temperatures  of  the  liquids  compared, 
approximate  30°  C. 

To  test  the  sensation  of  Pressure,  the  hand  or  other  part 
to  be  investigated  must  be  entirely  at  rest,  and  supported  on 
a  horizontal  surface.  The  weights  used  must  be  moderate — 
from  a  pound  to  four  or  five  pounds ;  in  which  case  it  will  be 
found  that  a  difference  between  two  weights  of  one-thirtieth 
can  be  detected. 

For  testing  the  sensation  of  locality  in  any  part  of  the  sur- 
face of  the  body,  a  pair  of  compasses  is  used,  of  which  the 
points  are  provided  with  cork  sheaths,  having  smooth  blunt 
ends.  The  points  being  at  first  at  such  a  distance  that  when 
both  touch  the  skin  or  mucous  membrane  of  the  tongue,  they 
are  distinctly  felt  as  two,  they  are  gradually  brought  nearer 


SENSATION  AND  PERCEPTION.  3I 

until  the  two  impressions  blend  into  one.  The  smaller  the 
distance  at  which  this  happens,  the  finer  is  the  sensation  of 
locality  in  the  region  investigated.  Another  method  is  that 
of  interrogation.  The  observer  touches  the  skin,  and  asks 
the  observed  person  to  designate  the  locality  touched. 

The  sensation  of  muscular  exertion  is  tested  by  experi- 
ments, each  of  which  consists  in  lifting  in  succession,  two 
weights,  of  which  one  is  heavier  than  the  other  by  a  small 
but  perceptible  difference;  this  difference  is  diminished  at 
each  trial  until  it  can  no  longer  be  appreciated.  As  it  is 
essential  that  sensation  of  pressure  should  be  excluded,  the 
weight  to  be  estimated  must  in  each  trial  be  enclosed  in  a 
handkerchief,  of  which  the  corners  must  be  held  in  the  hand. 

For  the  investigation  of  the  sensation  of  taste  and  of  the 
limits  of  the  gustatory  region,  four  test  liquids  should  be  pre- 
pared, viz.,  saturated  solution  of  sulphate  of  quinine,  10  per 
cent,  solution  of  common  salt,  3  per  cent,  solution  of  sugar, 
and  0"i  per  cent,  solution  of  citric  acid.  These  liquids  re- 
present the  four  fundamental  sensations,  each  of  which  may 
be  tested  separately,  or  two  alternately.  In  each  experiment 
a  camel-hair  pencil  is  dipped  in  the  liquid,  drained  by  touch- 
ing it  with  filter  paper,  and  applied  for  a  moment  to  the  sur- 
face. To  secure  freedom  from  bias  on  the  part  of  the  observed 
person,  trials  should  be  made  in  which  tasteless  liquids,  or 
liquids  of  different  tastes  are  alternated  in  various  orders, 
care  being  taken  to  irrigate  the  surface  between  each  trial 
and  the  following  one,  with  water. 

The  voltaic  sensations  of  taste  are  experienced  when  two 
zinc  plates,  which  form  the  terminals  of  a  Grove's  element, 
are  applied  respectively  to  the  upper  and  under  surface  of 
the  tongue  as  far  back  as  possible.  As  the  effect  differs  ac- 
cording to  the  direction  of  the  current,  a  reversing  key  must 
be  introduced  into  the  circuit. 


Part  II. 
DEMONSTRATIONS. 

I. — Mode  of  Measuring  and  Recording  the  Arterial 

Pressure. — Use  of  Recording  Apparatus. 

The  instrument  used  is  called  a  kymograph.  The  arterial 
cannula  is  a  T-shaped  tube  of  glass.  By  its  stem,  it  is 
connected  with  the  manometer  (a  U-shaped  glass  tube  con- 
taining mercury).  One  branch  of  the  T  is  drawn  out  and 
bevelled  so  as  to  be  easily  introduced  into  the  artery :  to  the 
other  is  fitted  a  short  piece  of  india-rubber  tubing,  guarded 
by  a  steel  clip.  The  stem  of  the  cannula  communicates  with 
the  proximal  arm  of  the  manometer  by  an  unyielding  tube  of 
lead  or  gutta-percha.  The  proximal  arm  (that  connected 
with  the  cannula)  also  communicates  by  a  long  flexible  tube 
with  a  bottle  containing  solution  of  bicarbonate  of  sodium 
under  pressure.  The  manometer  is  fixed  to  the  recording 
apparatus,  so  that  its  oscillations  are  inscribed  on  the  moving 
surface.  This  is  effected  by  means  of  a  style  carried  by  a 
vulcanite  rod,  which  floats  on  the  surface  of  the  mercury  in 
the  distal  (open)  limb  of  the  manometer.  The  recording 
cylinder  is  driven  by  clockwork;  it  is  either  covered  with 
smoked  glazed  paper,  or  is  fed  by  an  endless  roll  of  paper, 
in  which  case,  a  sable  pencil,  charged  with  coloured  ink,  is 
substituted  for  the  style.  The  paper  surface  in  either  case 
moves  at  a  uniform  rate  of  20  inches  per  minute. 

The  artery  used  is  the  carotid  of  the  rabbit.      The  distal 
end  of  the  prepared  part  of  the   vessel   is   ligatured.     The 


USE  OF  RECORDING  APPARATUS.        33 

proximal  end  is  temporarily  closed  by  a  spring--clip.  The 
vessel  having-  been  opened  near  the  ligature,  the  cannula  is 
introduced  and  secured  in  its  place  by  a  second  ligature,  its 
drawn-out  end  being  directed  towards  the  heart.  This  done, 
the  guttapercha  tube  of  the  manometer  is  connected  with  the 
stem  of  the  cannula,  and  the  whole  system  filled  with  solution 
of  sodic  bicarbonate  under  a  pressure  of  about  four  inches  of 
mercury.  On  removing  the  clip  on  the  artery,  communica- 
tion is  established  between  the  arterial  system  and  the  mano- 
meter, which  now  records  the  variations  of  arterial  pressure. 
The  tracing-  exhibits  larger  (respiratory)  undulations,  on  each 
of  which  many  smaller  undulations  Ccardiac  pulsations)  are 
inscribed.  It  shows  (i)  that  each  contraction  of  the  left 
ventricle  produces  a  momentary  increase  of  arterial  pres- 
sure; (2)  that  the  pressure  increases  after  each  inspiration, 
and  sinks  in  the  interval ;  (3)  that  during  the  rise  of  pres- 
sure the  pulsations  are  more  frequent  than  during-  the  fall. 
Excitation  of  the  Cardiac  end.  of  the  divided  Vagus  by 
faradisation,  produces  (if  weak  induction  currents  are  used) 
diminution  of  the  frequency  of  the  heart's  pulsation  and  of  the 
arterial  pressure.  If  strong-er  currents  are  used,  the  heart  is 
arrested  in  diastole. 

[N.B. — In  each  of  the  Demonstrations,  I.,  II.,  and  III.,  a 
rabbit  is  used,  which  is  rendered  completely  insensible  by  a 
suitable  anaesthetic,  and  is  killed  before  recovery.] 


II. — The  Normal  Respiratory  Movements.  Influence  of 
THE  Vagus  Nerve,  and  of  its  Centre.  Apn(ea  and 
Dyspncea. 

The  motions  of  a  metal   plate  which   is  kept  in  constant 
contact  with  the  posterior  surface  of  the  central  tendon  of  the 


34  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

diaphragm  of  the  rabbit,  by  the  pressure  of  a  spring,  are 
communicated  by  a  long  steel  wire  to  the  vertical  arm  of  a 
bell-crank  lever.  The  horizontal  arm  of  the  lever  is  pro- 
longed, and  bears  a  style  by  which  an  enlarged  record  of 
the  respiratory  motion  of  the  diaphragm  is  inscribed  on  the 
cylinder  of  the  recording  apparatus.  The  rate  of  movement 
of  the  cylinder  is  the  same  as  in  the  last  demonstration. 

The  inspiratory  contraction  of  the  diaphragm  is  expressed 
by  the  descent  of  the  writing  style,  its  relaxation  by  the 
ascent,  w^hich  is  at  first  rapid,  but  afterwards  more  gradual. 

Apnoea. — When  by  excessive  artificial  respiration  the  circu- 
lating blood  becomes  overcharged  with  oxygen,  all  respiratory 
movement  ceases.  On  discontinuing  the  injections  of  air, 
the  respirations  after  a  time  begin  again  ;  at  first  they  are 
scarcely  perceptible,  but  each  exceeds  its  predecessor  in 
extent,  until  the  normal  is  reached. 

Dyspnoea.— When  an  atmosphere  containing  an  inadequate 
percentage  of  oxygen  is  respired,  the  opposite  effect  to  that 
described  above  is  produced.  The  respirations  become  more 
ample  and  more  frequent,  and  the  auxiliary  muscles  are 
brought  into  action.  No  such  effect  is  produced  by  an 
atmosphere  containing  as  much  as  ten  per  cent,  of  COj, 
provided  that  the  supply  of  oxygen  is  sufficient. 

Excitation  of  the  Superior  Laryngeal  Nerve.— Excitation 
of  the  central  end  of  the  trunk  of  the  superior  laryngeal  nerve 
by  faradisation,  arrests  the  respiratory  movements,  the  dia- 
phragm becoming  stationary  in  the  position  of  expiration. 
When  extremely  feeble  currents  are  used,  rhythmical  move- 
ments may  continue  at  long  intervals.  Introduction  of  irritant 
gases  or  vapours  into  the  larynx  produces  similar  effects. 

Similar  excitation  of  the  central  end  of  the  divided  vagus, 
below  the  cricoid  cartilage,  produces  effects  which  differ  ac- 


FUNCTIONS    OF    VASCULAR    NERVES.  35 

cording-  to  the  strength  of  the  induction  currents  employed. 
When  currents  of  moderate  strength  are  used,  the  diaphragm 
remains,  during  the  excitation,  in  the  position  of  inspiration, 
the  state  of  contraction  being,  however,  usually  interrupted 
by  momentary  relaxations  at  short  intervals. 


III. — Functions  of  Vascular  Nerves. 

Constricting  Nerves.— Division  of  the  trunk  of  the  sympa- 
thetic opposite  the  cricoid  cartilage,  is  followed  by  dilatation 
of  the  central  artery  of  the  lobe  of  the  ear  on  the  same  side, 
and  increase  of  vascularity.  On  comparing  the  temperature 
of  the  congested  lobe  with  that  of  the  other  side,  it  is  found  to 
be  two  or  three  degrees  higher.  The  pupil  of  the  same  side 
is  more  contracted  than  the  opposite  one.  Excitation  of  the 
end  next  the  superior  ganglion  produces  constriction  of  the 
central  artery,  and  abolishes  the  congestion  of  the  lobe. 

Dilating  Nerves.— Excitation  of  the  central  end  of  the 
great  auricular  nerve  (or  of  the  posterior  auricular)  pro- 
duces temporary  vascular  changes,  which  are  identical  with 
those  permanently  produced  by  section  of  the  sympathetic. 

Depressor  Nerve.— Excitation  of  the  central  end  of  the 
divided  depressor  occasions  general  diminution  of  arterial 
pressure  (dependent  on  dilatation  of  the  blood-vessels  sup- 
plied by  the  splanchnic  nerves).  If  the  vagi  have  been 
previously  divided,  the  diminution  of  pressure  is  not  associ- 
ated with  any  change  in  the  frequency  of  the  contractions  of 
the  heart. 


D2 


36  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 


IV. — Movements  of  Circulation   and    Respiration    in    Man. 

I.  The  Cardiograph  and  Sphygmograph.— fa^  Two  re- 
ceiving" tympana  (cardiographs)  are  used.  One  is  applied  to 
the  seat  of  the  cardiac  impulse,  the  other  to  the  carotid  artery. 
The  two  recording  tympana  with  which  these  are  severally 
connected,  inscribe  the  motion  of  the  heart  and  that  of  the 
artery  respectively,  on  the  same  cylinder.  The  arterial  ex- 
pansion follows  that  of  the  heart  at  an  interval  of  about 
eig-ht-hundredths  of  a  second.  The  duration  of  the  ventri- 
cular impulse  is  about  three-tenths  of  a  second. 

(h)  The  sphygmograph  having  been  adjusted  so  as  to 
record  the  radial  pulse,  a  receiving  tympanum  on  the  carotid 
is  connected  with  a  recording  tympanum  attached  to  the 
frame  of  the  sphygmograph,  so  that  its  lever  writes  on  the 
same  surface  as  that  of  the  sphygmograph.  The  interval  of 
time  between  the  impulse  of  the  carotid  and  that  of  the  radial 
is  about  the  same  as  that  between  the  carotid  and  the  heart. 

2.  The  Stethograph.— The  changes  of  form  of  the  thorax 
in  respiration  are  investigated  by  the  measurement  of  the 
diameters  of  the  chest.  The  most  important  diameters  are, 
the  antero-posterior  (from  upper  end  of  sternum  to  third 
dorsal  spine,  150  millims.,  and  from  lower  end  of  sternum 
to  eighth  spine,  200  millims.)  ;  the  transverse  (at  the  eighth 
rib,  about  230  millims.).  These  measurements  refer  to  an 
adult  male,  as  taken  during  the  respiratory  pause.  The  first 
of  these  diameters  increases  about  a  millimeter,  the  second 
about  two  millimeters,  and  the  third  about  two  and  a  half  in 
ordinary  tranquil  inspiration.  These  measurements,  when 
recorded  by  the  stethograph,  yield  the  "  respiratory  curve." 


ELECTROMOTIVE    PHENOMENA    OF    MUSCLE.         2>7 


V. — Electromotive  Phenomena  of  Muscle. 

The  most  important  instrument  used  is  a  Thomson's 
Reflecting  Galvanometer,  of  hig-h  resistance,  the  terminals 
of  which  are  connected  by  insulated  copper  wires  with 
non-polarisable  electrodes.  These  are  in  contact  by  their 
clay  plugs  with  the  two  surfaces  to  be  compared. 

To  the  needle  of  the  galvanometer  a  light  concave  mirror 
is  attached,  on  which  a  beam  of  light  falls  and  is  focussed, 
after  reflection,  on  a  divided  screen.  Thus  the  smallest 
deflection  of  the  needle  (by  which  any  electrical  diff"er- 
ence  between  the  two  contacts  is  indicated)  can  be  exactly 
measured.  By  means  of  a  suitable  shunt,  either  the  whole, 
a  tenth,  or  other  decimal  fraction  of  any  current  flowing 
through  the  circuit  can  be  led  through  the  galvanometer. 

The  scale-reading  of  the  galvanometer  is  proportionate  to 
the  current  passing  through  it,  but  afl^ords  no  indication  of 
the  difference  of  potential  between  the  two  surfaces  compared. 
For  this  purpose  it  is  necessary  to  balance  the  current  in  the 
galvanometer  circuit  due  to  the  electromotive  force  of  the 
muscle,  by  an  opposed  current  of  which  the  electromotive 
force  is  known.  The  instrument  used  for  this  purpose  is 
called  a  Compensator.  {See  fig.  4).  Two  blocks,  A  and  B, 
are  connected  by  a  wire.  They  are  also  in  connection  (i) 
with  the  two  poles  of  a  Standard  Battery  (Z>)  by  wires,  one 
of  which  passes  through  a  multiplier,  and  (2)  by  two  other 
wires,  one  of  which  passes  through  a  rheostat,  with  the  corre- 
sponding poles  of  a  battery  of  several  cells.  This  must  be  of 
such  strength  that  when  the  resistance  of  the  rheostat  is  made 
as  small  as  possible,  the  battery,  D,  is  over  compensated. 
The  resistance  is  then  increased  until  the  galvanometer  (g) 


38     PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 


is  at  zero.  Under  these  conditions  the  difference  of  potential 
between  A  and  B  is  equal  to  the  electromotive  force  of  the 
standard  cell.  If,  therefore,  as  shown  in  the  diagram,  a  part  of 
the  rheochord  wire,  Aa,  included  in  the  same  circuit  with  the 
galvanometer  G,  is  of  such  length  that  the  current  due  to  the 
electromotive  force  of  the  muscle,  is  exactly  balanced,  so  that 
there  is  no  deflection,  the  difference  of  potential  between  the 
two  led  off  surfaces/^  and  m,  is  to  the  e.m.  f.  of  the  standard 
cell,  as  the  distance,  Aa,  is  to  the  whole  length  of  the  wire. 

All  of  the  electromotive  properties  of  muscle  may  be  de- 
monstrated more  advantageously  and  strikingly  with  the  aid 
of  the  capillary  electrometer,  than  by  the  galvanometer,  first 
because  it  indicates  differences  of  potential,  irrespectively  of 
resistance,  and  secondly  because  transitory  changes  in  the 
electrical  relations  of  two  "led  off"  surfaces  (such  as  those 


ELECTROMOTIVE    PHENOMENA    OF    MUSCLE.         39 

which  accompany  the  excitatory  process  in   muscle)   can   be 
observed  by  it. 

1.  Electromotive  Phenomena  of  Musele.—The  g^astro- 
cnemius  muscle  of  the  frog"  is  used.  One  of  the  electrodes  is 
in  contact  with  the  convex  surface  of  the  muscle  near  its 
upper  end,  the  other  with  the  expansion  of  the  tendo  Achillis. 
In  this  arrangement  the  surface  of  the  tendon  is  negative  to 
that  of  the  muscle. 

2.  On  exciting  the  muscle  by  faradising  its  nerve,  a  deflec- 
tion takes  place  in  such  a  direction  as  to  indicate  that  the 
electrical  difference  between  the  two  surfaces  is  diminished. 
After  excitation  the  needle  resumes  its  former  position. 

If  the  capillary  electrometer  is  used,  it  is  seen  that  the 
mercury  column  oscillates  during  the  period  of  diminution, 
and  that  the  number  of  oscillations  per  second  corresponds  to 
the  number  of  excitations  to  which  the  muscle  is  subjected  in 
the  same  time. 

3.  The  electrode  in  contact  with  the  tendinous  expansion  is 
now  brought  near  to  its  fellow,  so  that  both  contacts  are  now 
muscular.  They  are  nearly  isoelectrical.  On  injuring  the 
lower  of  the  two  contacts  mechanically,  or  by  heat,  it  be- 
comes at  once  strongly  negative.  On  excitation  of  the  nerve 
by  induced  currents,  the  negativity  diminishes  as  before. 

4.  Electromotive  Phenomena  of  the  Ventricle  of  the 
Prog  Heart.— A  Stannius'  heart  preparation  {See  Part  II.,  5) 
is  "led  off""  by  contacts  at  its  apex  and  base.  If  the 
heart  is  uninjured,  these  surfaces  will  be  found  to  be 
nearly  isoelectrical.  On  injuring-  either  surface  it  becomes 
negative. 

2.  A  normally  contracting  heart  is  led  off  by  contacts 
similarly  situated.  Each  contraction  is  accompanied  by  a 
deflection  of  the  needle,  indicating  that  the  apex  becomes  first 


40  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

positive  then  negative.     By  injuring  the  apex,  mechanically  or 
otherwise,  the  deflection  becomes  entirely  positive. 

3.  A  ventricle  preparation  (Part  II.,  6)  is  led  off  at  apex  and 
cut  surface.  During  contraction,  the  effect  is  similar,  but  the 
negative  deflection  is  much  larger. 

4.  A  ventricle  apex  preparation  (which  does  not  contract 
spontaneously)  is  led  off  as  above.'  Its  cut  surface  is  at  first 
strongly  negative  to  the  apex.  On  excitation  at  the  base  by 
a  single  induction  shock,  the  ventricle  contracts,  its  contrac- 
tion being  accompanied  by  a  deflection  indicating  that  the 
apex  becomes  negative. 


Part  III. 

ELEMENTARY   EXERCISES   IN   CHEMICAL    PHYSIO- 
LOGY. 

I. — Starch,  Dextrin,  Dextrose,  Fat. 

1 .  Starch  is  insoluble  in  cold  water. 

2.  It  dissolves  imperfectly  in  hot  water;  the  liquid  so 
obtained  is  opalescent. 

3.  It  g-ives  a  blue  colour  with  iodine,  which  vanishes  when 
the  liquid  is  heated,  but  returns  on  cooling,  if  the  heating  has 
not  been  prolonged. 

4.  Dextrin  is  soluble  in  water. 

5.  The  solution  gives  a  red-brown  colour  with  iodine, 
which  vanishes  on  heating. 

6.  Commercial  Grape-sugar  is  a  yellowish-brown,  crumbly 
substance,  which  is  readily  soluble  in  water.  Its  solution  is 
usually  slightly  coloured,  and  reduces  alkaline  solutions  of 
cupric  hydrate. 

7.  The  Copper  test.— To  a  small  quantity  of  ten  per  cent, 
solution  of  cupric  sulphate,  add  about  5  c.c.  of  the  liquid  to 
be  tested ;  then  solution  of  caustic  potash  drop  by  drop  until 
the  solution  is  clear,  and  heat  gradually.  If  dextrose  is 
present,  the  blue  colour  vanishes,  and  a  yellow  precipitate 
appears  of  cuprous  hydrate,  or  a  red  precipitate  of  cuprous 
oxide. 

8.  Conversion  of  starch  into  reducing  sugar.  Boil  about 
50  c.c.  of  starch  solution  in  a  flask  with  a  drop  of  25  per 
cent,  sulphuric  acid  for  five  minutes.  The  liquid  becomes 
limpid.  It  contains  in  addition  to  dextrose  much  soluble 
starch  (Amidulin) . 


42  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

9.  Fat- Lard  is  insoluble  in  water.  By  boiling  with 
potash  it  yields  a  solution  of  soap. 

10.  Decompose  the  solution  by  adding  a  few  drops  of 
dilute  sulphuric  acid.  On  heating,  a  layer  of  fatty  acid 
collects  on  the  surface. 

1 1 .  Microscopical  Preparations.— Starch  grains ;  their  dis- 
integration by  hot  water;  action  of  iodine  on  them.  Crystal- 
line forms  of  fatty  acids. 

II. — Milk,  Flour,  Bread. 

1.  Milk  has  (in  London)  usually  an  acid  reaction,  and  a 
specific  gravity  of  from  1025  to  1030.  After  removal  of  the 
cream,  the  specific  gravity  is  higher. 

2.  Milk  contains  fat,  sugar,  and  proteids. 

a.  Proteids.— Heat  about  50  c.c.  of  milk  to  40°  C.  in  a  flask. 
Add  a  few  drops  of  rennet- extract,  keeping  the  milk  at  the 
same  temperature  until  a  coagulation  is  formed. 

b.  Dilute  5  c.c.  milk  with  eight  or  nine  times  as  much 
water,  acidulate  with  a  drop  or  two  of  acetic  acid,  and  warm 
as  before.     Strain  off  the  coagulated  casein  through  muslin. 

c.  When  milk  is  filtered  under  pressure  through  a  porous 
disk,  its  casein,  being  particulate,  remains  behind.  The 
clear  filtrate  contains  lactose  (milk-sugar)  and  salts. 

d.  Sugar.— The  strained  liquid  from  a  (whey)  contains 
lactose,  which,  like  dextrose,  reduces  metallic  oxides.  Apply 
the  copper  test  (I.,  7). 

e.  Fat.— The  coagulated  casein  contains  much  fat  (butter) 
which  can  be  extracted  by  ether.  The  ether  extract,  when 
evaporated  on  paper,  leaves  a  greasy  stain. 

3.  Flour.— Wash  about  a  desert-spoonful  of  sound  flour  in 
a  muslin  bag. 


ALBUMIN.  43 

a.  A  milky  liquid  passes  through  containing-  much  starch 
(I.,  3)  but  no  sugar. 

b.  After  washing  for  some  minutes,  a  sticky  and  tenacious 
material  remains  on  the  muslin,  which  can  be  collected;  this, 
after  further  washing,  forms  an  elastic  mass  (gluten)  which 
can  be  drawn  out  into  threads,  and  on  burning,  gives  off  the 
smell  of  burnt  feathers  characteristic  of  a  proteid. 

4.  Bread. — Digest  with  warm  water.  The  extract  contains 
starch  (I.,  3)  and  dextrose  (I.,  7).  The  residue  consists  prin- 
cipally of  starch  and  gluten. 


III. — Albumin  and    its   Acid    and    Alkaline   Modifications. 

r.  Albumin.— White  of  egg  (albumen)  when  diluted  with 
water,  strained  and  filtered,  yields  a  faintly  opalescent  liquid. 
This  liquid  contains  a  proteid  body,  albumin,  which  diffuses 
through  an  animal  membrane  with  great  difficulty  (V.,  3). 

2.  Such  a  liquid,  containing  5  per  cent,  of  albumen,  is  to  be 
used  in  the  following  experiments.  It  coagulates  on  heating 
at  about  70°  C.  if  neutral. 

3.  To  some  of  the  liquid  add  a  few  drops  of  0"i  per  cent, 
solution  of  caustic  potash,  and  warm  gently  for  two  or  three 
minutes.  Boil.  The  liquid  will  no  longer  coagulate,  the 
albumin  having  been  transformed  into  the  alkaline  modifica- 
tion (alkali-albumin). 

4.  In  a  similar  way  treat  another  portion  with  a  few  drops 
of  very  dilute  sulphuric  acid  (O'l  per  cent.).  Warm  very 
gently  for  not  less  than  five  minutes.  On  boiling  no  coagu- 
lation occurs,  the  albumin  having  passed  into  its  acid  modifi- 
cation (acid-albumin,  syntonin.) 

5.  Cool  some  of  the  liquid  obtained  in  3.  Colour  it 
with    litmus   solution,    and   add    carefully   very   dilute    acid. 


44  PR.\CTICAL    EXERCISES    IN    PHYSIOLOGY. 

A   precipitate    falls    on    neutralization,    which   is    soluble   in 
excess  of  acid. 

6.  Make  a  similar  experiment  with  the  liquid  obtained  in 
4,  substituting  w^eak  solution  of  potash  for  weak  acid.  A 
similar  precipitate  occurs  on  neutralization,  which  is  soluble 
in  excess. 

7.  Take  three  portions,  of  5  c.c.  each,  of  the  original 
liquid  in  three  test-tubes,  and  colour  them  wath  litmus. 
Dilute  the  c  i  per  cent,  acid  about  5  times,  and  add  a  drop 
of  it  to  one  of  the  portions ;  to  another  add  a  drop  of  potash 
solution  similarly  diluted.  Heat  all  three  tubes  gradually, 
and  note  the  temperature  at  which  each  coag^jlates. 

8.  Make  alkali-albumin  solution  as  in  3.  Divide  it  into 
two  equal  parts.  To  one  add  two  or  three  drops  of  10  per 
cent,  solution  of  sodic  phosphate.  Colour  both  with  litmus, 
and  neutralize  with  w-eak  acid.  The  portion  without  sodic 
phosphate  is  precipitated.  The  other  portion  is  not  precipi- 
tated until  enough  acid  has  been  added  to  convert  the  sodic 
phosphate  present  into  acid  sodic  phosphate. 


TV. — Chakacteristics  of  Proteids. — Peptic  Digestion. 

I .  Tests  for  proteid  bodies  in  solution. 

a.  To  some  of  the  albuminous  liquid  referred  to  in  TIL,  2, 
add  strong  nitric  acid.  The  precipitate  obtained  turns  yel- 
low on  boiling. 

6.  Cool  the  liquid  in  a  and  add  strong  ammonia.  The  pre- 
cipitate assumes  an  orange  tint  (Xanthoprotein  reaction). 

c.  To  another  portion  add  Millon's  reagent.  (Mercury  is 
dissolved  in  its  own  weight  of  strong  nitric  acid.  The  solution 
so  obtained  is  diluted  with  twice  its  volume  of  water.     The 


PROTEIDS.  45 

decanted  clear  liquid  is  Millon's  reagent).     A  precipitate  is 
formed  which  turns  dull  red  on  boiling. 

d.  To  a  third  portion  add  solution  of  potassic  ferrocyanide, 
and  a  drop  of  acetic  acid.     A  white  precipitate  appears. 

e.  Introduce  a  fourth  portion  of  the  liquid  into  a  test-tube 
containing"  one  drop  of  ten  per  cent,  solution  of  cupric  sul- 
phate. On  adding  solution  of  potash,  a  violet  colour  is 
obtained  (compare  v.,  2,  b'). 

2.  Serum-globvilin. 

a.  Neutralize  5  c.c.  of  serum  with  a  few  drops  of  O'l  per 
cent,  sulphuric  acid.  Dilute  with  about  75  c.c.  of  water,  and 
allow  the  precipitate  to  settle.  The  precipitate  is  insoluble 
in  water,  but  soluble  in  excess  of  acid. 

b.  Dilute  5  c.c.  of  serum  with  75  c.c.  of  water,  and  pass 
through  it  a  stream  of  CO,.    The  liquid  becomes  turbid  as  in  a. 

c.  Repeat  b  without  dilution.     No  precipitate  is  formed. 

d.  Add  to  a  saturated  solution  of  sulphate  of  magnesium  a 
small  quantity  of  serum.     A  copious  precipitate  is  formed. 

e.  Pour  over  some  fibrin  contained  in  a  watch-glass  some 
solution  oL  pero.xide  of  hydrogen.  Bubbles  of  oxygen  are 
given  off.  If  some  tincture  of  guaicum  be  added,  a  blue 
colour  is  developed.  Gluten,  potato  peelings,  and  many 
other  substances  develop  a  blue  colour  under  the  same  con- 
ditions. 

3.  Peptic  Digestion. 

a.  Introduce  some  fibrin  into  a  test-tube,  and  just  cover  it 
with  0-2  per  cent,  solution  of  HCl.  Allow  it  to  stand  for 
forty-five  minutes  in  a  water-bath  at  from  35°  to  3S'  C.  At 
the  end  of  this  time  the  fibrin  is  swollen  and  transparent,  but 
has  not  dissolved. 

b.  Repeat  a,  using  instead  of  hydrochloric  acid,  water  to 
which  a  drop  of  glycerine  extract  of  gastric  mucous  mem- 
brane has  been  added. 


46  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

The  fibrin  remains  unaltered, 

c.  Repeat  a,  adding-  a  drop  of  the  same  extract  to  the  acid 
liquid.     The  fibrin  dissolves  gradually. 

d.  Colour  with  litmus  the  liquid  obtained  in  c.  Neutralize 
carefully  with  weak  solution  of  caustic  potash  (III.,  6).  The 
acid  albumin  formed  during  the  first  stage  of  digestion  is  pre- 
cipitated. 


V. — Pancreatic  Digestion. — Amylolytic  Ferments. — 
Glycogen. 

I.  Pancreatic  Digestion. 

a.  Introduce  5  c.c.  of  one  per  cent,  solution  of  sodium 
carbonate,  to  which  a  couple  of  drops  of  glycerine  extract 
of  pancreas  have  been  added,  into  each  of  two  test-tubes. 
Boil  one  of  them  and  allow  it  to  cool.  Add  some  boiled  fibrin 
to  each,  and  place  them  both  in  the  water-bath  at  35°  C. 
Compare  the  changes  produced  with  those  observed  in  pep- 
tic digestion  (IV.,  3,  c). 

b.  Examine  the  liquid  product  of  a  pancreatic  digestion, 
previously  prepared  by  allowing  a  finely  divided  ox  pancreas 
to  digest  itself  in  a  i  per  cent,  solution  of  sodium  carbonate. 
It  is  alkaline,  and  may  have  a  characteristic  and  offensive 
odour. 

c.  Boil  some  of  this  liquid  after  acidulating  slightly.  Albu- 
min is  coagulated. 

d.  Colour  another  portion  with  litmus,  and  neutralize 
carefully  (III.,  5);  alkali-albumin  is  precipitated. 

e.  In  a  liquid  obtained  by  concentrating  the  product  above 
referred  to,  after  having  separated  the  greater  part  of  the 
proteids  contained  in  it,  test  for  Tyrosin  by  adding  Millon's 


GLYCOGEN.  47 

reagent,  and  boiling'.     The   presence  of  Tyrosin   is  indicated 
by  the  reddish  colour  assumed  by  the  liquid. 

f.  From  such  liquids  Leucin  usually  separates  on  concentra- 
tion, and  can  be  recognized  under  the  microscope  by  its 
crystalline  form. 

2.  Peptones.— A  solution  obtained  either  by  pancreatic  or 
peptic  digestion  can  be  used. 

a.  The  solution  yields  no  precipitate  either  by  boiling  or 
by  neutralization,  but  is  precipitated  by  alcohol. 

b.  When  concentrated  and  treated  as  in  IV.,  i,  e,  it  gives 
a  red  instead  of  a  violet  colour. 

The  liquid  product  of  the  slow  putrefaction  of  proteids 
resembles  in  most  respects  that  of  pancreatic  digestion.  To 
the  latter,  the  presence  of  septic  organisms  is  not  essential. 

c.  Peptone,  although  more  diffusible  than  other  proteids, 
does  not  diffuse  through  parchment  paper. 

3.  Indiffusibility  of  Proteids.— Suspend  a  parchment  paper 
tube  containing  diluted  blood,  in  a  beaker  of  distilled  water, 
so  that  the  two  open  ends  are  above  the  surface.  The  col- 
ouring matter  and  proteids  do  not  pass  through  the  mem- 
brane. The  soluble  salts  pass  through  readily,  and  their 
presence  in  the  water  can  be  recognized  by  the  usual  tests. 

4.  Amylolytic  Ferments.— Prepare  some  starch  solution 
and  ascertain  that  it  contains  no  dextrose  (I.,  2  and  8).  To 
another  portion  add  saliva,  and  place  the  tube  containing  the 
mixture  in  a  water-bath  at  from  35°  to  38°  C.  After  a  short 
time,  the  product  will  be  found  to  contain  dextrose. 

5.  Glycogen. 

a.  To  an  extract  of  liver  (prepared  by  extracting  the  per- 
fectly fresh  organ  with  boiling  water  after  washing)  add  a 
solution  of  iodine  in  potassic  iodide.  The  liquid  assumes  a 
red  colour  identical  with  that  yielded  under  similar  circum- 
stances by  dextrine  {^See  I.,  5). 


48     PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

b.  Repeat  4,  substituting  extract  of  liver  for  starch  paste, 
using  the  same  precautions. 


VI.— Bile. 

1.  Observe  colour  and  reaction  of  ox  bile.  It  is  usually 
brown.  Neutralize  and  boil  in  a  test-tube.  Bile  does  not 
contain  albumin. 

2.  Add  a  few  drops  of  bile  to  methylated  spirit.  Mucin 
is  precipitated. 

3.  Prepare  a  solution  of  syntonin  (III.,  4)  by  digesting- 
albumin  in  water  containing  0*2  per  cent,  of  hydrochloric 
acid.  On  the  addition  of  a  drop  of  bile,  the  mixture  curdles 
en  masse.  If  a  large  quantity  of  bile  be  added,  little  or  no 
precipitate  may  be  formed,  the  liquid  being  rendered  alkaline. 

4.  Boil  bile  with  three-times  its  bulk  of  strong  hydrochloric 
acid  for  ten  minutes.  The  bile  is  decomposed  into  bile-resin 
(cholic  acid  with  colouring  matter)  and  glycin  and  taurin,  the 
two  last-mentioned  substances  remaining  in  solution. 

5 .  Pettenkofer's  Test  for  Cholic  acid.— Spread  a  drop  of 
bile  in  a  thin  film  on  a  white  porcelain  capsule.  Mix  with  a 
drop  of  strong  solution  of  cane-sugar.  Add  concentrated 
sulphuric  acid  drop  by  drop,  and,  if  necessary,  warm.  A 
deep  purplish-red  colour  appears. 

6.  Repeat  the  test  with  an  alcoholic  solution  of  bilin.  The 
same  colour  is  produced. 

7.  Gmelin's  Test  for  the  colouring  matter.  Spread  a 
drop  of  bile  in  a  thin  film  on  a  white  porcelain  capsule. 
Allow  a  drop  of  strong  nitric  acid  to  fall  into  the  middle  of 
the  film  and  observe  the  effect.  The  drop  becomes  sur- 
rounded by  rings  of  green,  blue,  red^  and  yellow,  in  the 
order  in  which  they  have  been  named.      Consequently,  Jhe 


URINE.  49 

gfreen,  which  is  first  formed,  is  eventually  farthest  from  the 
drop  of  acid.  If,  instead  of  allowing-  the  liquid  to  remain 
undisturbed,  the  acid  be  mixed  with  the  bile,  the  liquid  passes 
through  the  same  tints,  in  the  same  order. 

8.  Warm  a  little  nitric  acid  in  a  test  tube.  Incline  the  tube 
and  pour  bile  down  the  side,  so  as  to  form  a  layer  over  the 
acid.  The  colours  appear  as  in  7,  at  the  line  of  contact  of  the 
two  liquids. 

9.  Cholesterin.  An  ethereal  extract  of  gall  stones  yields, 
on  evaporation,  crystals  of  cholesterin,  which,  when  dropped 
into  warm  sulphuric  acid,  dissolve  with  a  red  colour.  The  resi- 
due, insoluble  in  ether,  consists  of  colouring  matter  and  mucin. 

VII.— Urine,     (i) 

1.  Observe  reaction  and  colour. 

2.  Determine  the  specific  gravity  either  by  weighing-  or 
with  the  urinometer.     Observe  the  effect  of  temperature. 

3.  Compare  fresh  with  stale  urine  as  regards  appearance, 
smell,  and  reaction. 

4.  Sulphates.  Add  baric  chloride  after  acidifying-  with 
hydrochloric  acid.  A  white  precipitate  of  baric  sulphate  ist 
formed. 

5.  Chlorides.  Add  argentic  nitrate  after  acidifying  with 
nitric  acid.  A  white  curdy  precipitate  of  argentic  chloride  is 
produced. 

6.  Phosphates.  Add  ammonic  molybdate  to  urine  which 
has  been  mixed  with  half  its  volume  of  nitric  acid.  Boil.  A 
yellow  crystalline  precipitate  falls. 

7.  Urea.  To  urine  evaporated  to  one-third,  add  a  drop  of 
nitric  acid  in  a  watch-glass.  Glistening  scales  of  urea  nitrate 
are  abundantly  formed  in  the  liquid. 


50  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

8.  Uric  Acid.  To  a  hundred  c.c.  of  urine  add  5  c.c.  of 
strong-  hydrochloric  acid.  Allow  the  liquid  to  stand  for  forty- 
eight  hours.  Dark  red  crystals  of  uric  acid  separate  from  the 
liquid. 

9.  Uroolirome.  Precipitate  about  50  c.c.  with  lead  acetate 
and  a  drop  of  ammonia.  Filter.  The  filtrate  is  colourless. 
Scrape  the  precipitate  from  the  filter  paper  into  a  capsule. 
Mix  with  a  few  drops  of  strong  sulphuric  acid  and  add  to 
the  pasty  mass  a  little  alcohol.  Filter.  The  yellow  filtrate, 
on  boiling-  with  excess  of  strong  sulphuric  acid,  turns  black. 
Dilute  the  acid  liquid  with  a  large  quantity  of  water.  The 
tiromelanine  which  separates  in  flocks  is  characterized  by  its 
extreme  solubility  in  ammonia.  It  can  be  precipitated  from 
its  solution  in  ammonia  by  sulphuric  acid. 

10.  Indigo.  To  500  c.c.  of  urine  add  250  c.c.  of  pure 
hydrochloric  acid.  Allow  the  liquid  to  stand  twenty-four 
hours.  A  coppery  scum  floats  on  the  surface.  Filter. 
Treat  the  filter  first  with  ammonia  to  extract  the  urome- 
lanine,  secondly  with  cold  alcohol,  which  acquires  thereby 
a  red  colour.  On  boiling  the  residue  in  alcohol,  a  blue 
solution  is  obtained,  which  exhibits  the  absorption  spectrum 
of  indigo-blue. 

N.B. — In  consequence  of  the  large  quantities  which  must  be 
used,  this  experiment  cannot  be  carried  out  by  each  student. 

VIII.— Urine.     (2) 

I .  Quantitative  determination  of  ITrea.  Urea  (CO  N3H4) 
when  decomposed  by  suitable  oxidizing-  agents,  yields  CO3  H^O 
and  N.  The  most  convenient  reagent  for  effecting  this  de- 
composition is  an  alkaline  solution  of  sodic  hypobromite. 
The  CO3  is  absorbed  by  caustic  soda.  The  nitrogen  which 
is  disengaged    is  collected  and  measured  in  a  suitable  ap- 


DUPRE  S    APPARATUS. 


51 


paratus.      Every  37-3  c.c.  of  nitrogen,  at  ordinary  pressure 

and    temperature,  corresponds  to    o*i  grm.    of  urea.      The 

hypobromite    solution    is    prepared    by    adding"    25    c.c.    of 

bromine  to  250  c.c.  of  a  solution   containing    100  grms.   of 

caustic  soda. 

Fig.  5. 


The  stopper  and  test-tube  represented  in  the  upper  left  hand  of  the  figure  takes  the  place 
of  the  stopper,  pipette  and  tube  e  j.     The  woodcut  has  been  kindly  lent  by  Dr.  Dupr6. 

Dupre's  apparatus  is  used.     Introduce   25    c.c.    of  hypo- 

E  2 


52  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

bromite  into  the  flask  c.  Measure  off  5  c.c.  of  urine  into  the 
test-tube,  and  close  the  flask  with  the  caoutchouc  stopper  to 
which  the  test-tube  is  attached.  Open  the  pinch-cock  d  and 
lower  the  measuring-  tube  a,  until  the  surface  of  the  water  is 
at  the  zero  point  of  the  graduation.  Close  the  pinch-cock 
and  raise  the  measuring  tube.  If  the  apparatus  be  tight, 
mix  the  urine  gradually  with  hypobromite  solution  by  inclin- 
ing" the  flask.  Finally,  tilt  the  flask  so  as  to  rinse  out  the 
test-tube  with  the  solution,  and  shake  well  for  a  few  seconds. 
Immerse  the  flask  in  a  vessel  containing  water  at  the  same 
temperature  as  that  in  the  jar.  At  the  same  time  lower 
the  measuring  tube.  After  two  or  three  minutes,  raise 
the  measuring  tube  again  until  the  surfaces  of  the  liquids 
inside  and  out  coincide.  Read  off  the  quantity  of  nitro- 
gen which  results  from  the  decomposition  of  the  5  c.c.  of 
urine. 

2.  Quantitative  determination  of  Phosphates. — When 
solution  of  uranic  nitrate  or  acetate  is  added  in  successive 
quantities  to  a  hot  solution  containing  phosphates,  previously 
acidified  with  acetic  acid,  the  whole  of  the  uranium  is  precipi- 
tated so  long  as  any  phosphate  remains  in  solution  as  uranic 
phosphate.  As  soon  as  an  excess  of  uranic  salt  is  present, 
it  can  be  detected  by  potassic  ferrocyanide,  which  gives  a 
brown  colour  with  uranic  salts. 

The  standard  uranic  nitrate  solution  contains  35*5  grammes 
in  a  litre.     One  c.c.  corresponds  to  0*005  gramme  PzO^. 

To  50  c.c.  of  urine  add  5  c.c.  of  a  solution  containing  100 
grammes  of  sodic  acetate  in  900  c.c.  of  water,  to  which  lOO 
c.c.  of  glacial  acetic  acid  have  been  added.  Heat  the  55  c.c. 
to  So"  C.  Add  the  uranic  nitrate  solution,  until  a  drop  of  the 
mixture  placed  on  a  white  porcelain  slab  gives  a  distinct 
brown  colour,  with  a  drop  of  potassic  ferrocyanide.     Note 


COLOURING  MATTER  OF  THE  BLOOD.      53 

the  quantity  of  solution  used,  and  calculate  therefrom  the  per- 
centage of  PjO^  in  the  urine.** 

IX. — The  Colouring  Matter  of  the  Blood. 

1.  Observe  the  solar  spectrum,  noting  the  positions  of  the 
dark  lines  D,  E,  b  and  F,  in  relation  to  the  colours.  Com- 
pare it  with  the  spectrum  of  a  gas  flame,  which  shows  no 
dark  lines. 

2.  Observe  the  spectrum  of  a  flame  coloured  with  sodic 
chloride,  noting  the  position  of  the  bright  yellow  line. 

3.  Oxy-hsemoglobin.— Introduce  defibrinated  blood  into  a 
test-tube,  and  observe  its  opacity  when  undiluted. 

(a)  Dilute  by  adding  five  to  ten  times  its  bulk  of  water. 
Place  the  test-tube  in  front  of  the  slit  of  the  spectroscope, 
direct  it  to  a  gas  flame.  The  only  light  which  passes  through 
is  that  of  the  red  end  of  the  spectrum. 

(b)  Add  water  until  the  green  appears.  Note  the  dark 
space  (absorption  band)  between  the  red  and  green. 

{c)  Dilute  still  further  until  the  yellow-green  light  is  dis- 
tinguishable in  the  middle  of  the  dark  space,  dividing  the 
single  broad  band  into  two. 

(d)  After  a  further  addition  of  water,  note  that  the  band 
nearest  the  D  line  is  somewhat  more  sharply  defined  than  the 

*  For  details  as  to  the  hypobromite  method,  see  Dupre's  original  paper  in 
the  journal  of  the  Chemical  Society,  1877,  vol.  i.  p.  534. 

The  method  for  the  determination  of  PgOg  is  practised  in  this  class  as  an 
example  of  a  volumetric  process.  For  other  methods  relating  to  the  urine 
see  Part  IV.  It  is  important  to  remember,  that  in  order  to  obtain  trustworthy 
results,  as  scrupulous  care  must  be  taken  in  the  measurement  and  collection 
of  the  urine  passed  during  the  period  of  observation  as  in  the  analytical  pro- 
cedures. 


54  PRACTICAL   EXERCISES   IN    PHYSIOLOGV, 

other.  The  spectrum  is  still  shortened  by  the  absorption  of 
its  violet  end. 

(e)  On  diluting-,  until  the  solution  is  almost  colourless,  two 
faint  bands  are  still  visible. 

(/)  Map  on  the  diagram  the  appearances  observed  in  3, 
b  and  d. 

4.  Reduced  Hsemoglobin. — To  some  blood  diluted  as  in  3, 
d,  add  a  drop  of  solution  of  ammonic  sulphide,  and  warm 
g-ently.  The  colour  becomes  purplish.  Place  the  tube  in 
front  of  the  slit  as  before,  and  observe  the  change  which  has 
occurred.  A  single  absorption  band,  with  ill-defined  edges, 
takes  the  place  of  the  two  bands  previously  observed.  Map 
its  position  on  the  diagram. 

5.  Alkaline  Hsematin  (Hsemocliroinogen). — Add  to  solu- 
tion of  blood,  rather  stronger  than  the  last,  a  drop  of  solu- 
tion of  caifliStic  potash.  Warm  gently ;  the  colour  completely 
changes.  An  absorption  band  appears  to  the  left  of  the  line 
D,  and  much  of  the  blue  end  of  the  spectrum  is  cut  off. 

6.  Reduded  Alkaline  Hsematin. — To  the  solution  obtained 
in  5  add  a  drop  or  two  of  ammonic  sulphide  and  warm 
gently.  Observe  the  change  of  colour.  Dilute  if  necessary. 
A  strongly  marked  band  is  seen  to  the  right  side  of  the  line 
D,  and  a  second  less  defined,  which  nearly  coincides  with  the 
line  E. 

7.  co-haemoglobin.— Blood  which  has  been  acted  upon  by 
carbonic  oxide  has  a  peculiar  cherry-red  colour.  The  two 
absorption  bands  have  nearly  the  same  position  as  those  of 
Oxy-haemoglobin,  but  no  change  is  produced  when  the  liquid 
is  treated  with  reducing  agents,  as  in  4. 


Part  IV. 

LABORATORY  EXERCISES  IN  CHEMICAL- 
PHYSIOLOGY. 

I. — Starch  and  its  Derivatives. 

1.  Prepare  potato  starch  by  grating  potatoes  into  water, 
stir  the  mixture  thoroughly,  and  allow  it  to  stand.  After 
partial  subsidence  pour  off  the  turbid  liquid  and  set  it  aside. 
Collect  the  white  deposit  of  starch,  mix  it  with  a  fresh  quan- 
tity of  water,  and  again  separate  it  by  subsidence  and  de- 
cantation. 

2.  Examine  the  product  microscopically.  Each  granule 
exhibits  concentric  markings,  which  become  more  distinct 
after  the  partial  action  of  solution  of  iodine.  In  the  dark 
field  of  the  polarisation  microscope,  each  shows  a  dark  cross 
on  a  bright  area. 

Digest  starch  in  saliva  at  45' — 50°  C.  for  3  hours.  Examine 
the  insoluble  residue  of  cellulose  before  and  after  treating 
with  solution  of  iodine. 

3.  Boil  a  portion  of  the  deposit  in  water  to  obtain  "starch 
solution"  and  filter.  Observe  that  the  liquid  is  opalescent 
and  that  when  a  beam  of  sunlight  passes  through  it  the  beam 
is  luminous.  When  viewed  transversely  through  a  Nicol's 
prism,  held  between  the  thumb  and  forefinger,  and  rotated, 
the  luminosity  appears  and  disappears  alternately.  Compare 
in  this  respect  solution  of  sulphate  of  quinine.  Starch  sola- 
tion  is  indiflfusible. 

4.  Grind  some  malt  in  a  coffee  mill,  extract  the  meal  with 


56     PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

four  or  five  times  its  volume  of  water  at  30°  C.  Concentrate 
the  extract  at  the  same  temperature  to  one  half. 

5.  Prepare  some  half  per  cent,  solution  of  starch,  to  part 
of  it  add  one  tenth  of  its  volume  of  malt  extract  and  place  the 
mixture  in  the  w^arm  chamber  at  70°  C.  From  time  to  time 
test  portions  of  the  liquid  with  solution  of  iodine.  As  soon  as 
the  liquid  remains  colourless  after  the  addition  of  the  iodine, 
arrest  further  change  by  boiling.  Concentrate  some  of  the 
product  and  pour  it  into  an  excess  of  alcohol.  The  precipi- 
tate is  achroodextrin,  maltose  remaining  in  solution.  Filter, 
evaporate  the  filtrate,  re-dissolve  the  residue  in  water,  and 
prove  the  presence  of  a  reducing  sugar. 

6.  Treat  the  remainder  of  the  half  per  cent,  solution  of 
starch,  with  one-tenth  of  its  volume  of  malt  extract  as  before, 
keeping  it  in  the  warm  chamber  for  three  hours.  Divide  the 
product  into  two  exactly  equal  parts ;  in  one  determine  the 
reducing  power  by  the  volumetric  method  described  below. 
Add  to  the  other,  two  per  cent,  of  concentrated  sulphuric 
acid,  boil  for  half  an  hour  in  a  flask ;  bring  the  liquid  to  its 
original  volume  by  the  addition  of  water,  and  estimate  the 
reducing  power  by  the  same  method. 

7.  Volumetric  estimation  of  sugar  by  Fehling's  method. 
Dissolve   34-639  grm.  of  pure  cupric  sulphate  in  about  20O 

c.c.  of  distilled  water,  also  dissolve  173  grm.  of  pure  double 
tartrate  of  potassium  and  sodium  (Rochelle  Salt)  in  500  to 
600  c.c.  of  a  solution  of  caustic  soda  of  i"i2  sp.  gr,,  mix  the 
two  solutions  and  dilute  to  a  litre.  10  c.c.  of  the  solution  so 
prepared  are  equivalent  to  "05  grm.  sugar. 

Dilute  10  c.c.  of  the  above  solution  with  40  or  50  c.c.  of 
water,  and  heat  to  boiling  in  a  white  porcelain  basin. 
Now  run  in  from  a  burette  the  sugar  solution  (previously 
diluted  so  as  not  to  contain  more  than  one  half  per  cent. 


MILK.  57 

of  sugar)  and  continue  to  do  so  until  the  blue  colour  of 
the  copper  solution  disappears,  i.e.  until  all  the  copper  is  re- 
duced. Rea.d  the  burette;  the  quantity  used  contains  05 
g-rm.  of  sug-ar,  whence  the  total  quantity  and  the  amount  of 
dilution  being  known,  the  total  quantity  of  sugar  may  be 
easily  calculated. 


II.— Milk. 

1.  Determine  the  sp.  gr.  of  a  sample  of  new  milk  with  the 
hydrometer.  Allow  it  to  stand  for  a  day  and  skim  off  the 
cream  and  determine  the  sp.  gr.  of  the  skimmed  milk.  Add 
water  until  it  is  reduced  to  the  original  sp.  gr.  Ascertain 
what  proportion  of  water  is  required  for  this  purpose. 

2.  Curdling  of  Milk. 

(a)  By  Rennet.— Warm  50  c.c.  of  milk  to  45°  C.  and  add 
20  drops  of  commercial  extract  of  rennet.  Set  it  aside  for  ten 
or  twenty  minutes;  the  coagulum  resembles  that  of  blood 
in  consistence;  filter  and  preserve  the  whey. 

{b)  By  Acid.— Dilute  milk  with  eight  volumes  of  water  at 
40°  C,  add  a  drop  or  two  of  acetic  acid.  Separate  the  curd 
which  forms  by  gentle  shaking,  and  filter;   keep  the  filtrate. 

Take  two  portions  of  the  curd  and  dissolve  one  in  weak 
caustic  soda,  and  the  other  in  lime  water.  Filter  both  from 
undissolved  particles,  and  add  a  little  rennet  to  both  filtrates. 
The  solution  in  lime  water  will  coagulate,  that  in  soda  will 
not, 

(<r)  Salt  Solution  Curd.— Treat  milk  with  twice  its  volume 
of  a  saturated  solution  of  common  salt  with  the  addition  of 
powdered  salt,  and  shake  thoroughly.  (This  is  best  effected  by 
a  machine ;  it  can,  however,  be  done  on  a  small  scale  by  shak- 
ing milk  in  a  test  tube  with  powdered  salt).  The  milk  coagu- 
lates, and  a  clear  filtrate  free  from  butter  and  casein  may  be 


58      PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

obtained.  Test  the  filtrate  for  sugar  and  coagulable  pro- 
teids  and  estimate  the  former  by  the  method  already  given. 

Dissolve  some  of  the  curd  in  water  and  add  rennet  to  the 
solution,  observe  that  it  coagulates. 

It  is  obvious  from  these  experiments  that  there  are  impor- 
tant differences  between  acid  and  rennet  curd,  and  that  cal- 
cium salts  are  accessory  to  the  action  of  rennet. 

{d)  Take  the  whey  from  two  equal  quantities  of  milk,  one 
prepared  with  rennet  the  other  with  acid.  Determine  the 
sp.  gr.  of  each,  and  the  amount  of  proteids.  Compare  the 
results  carefully. 

(e)  Neutralize  and  boil  acid  or  sweet  whey.  Filter  and 
concentrate.     Crystals  of  milk  sugar  may  be  obtained. 

(f)  Shake  milk  which  has  stood  for  several  weeks  in  the 
warm  chamber,  and  is  strongly  acid,  with  ether,  and  decant 
the  ethereal  extract,  allow  the  ether  to  evaporate,  and  ex- 
haust the  residue  with  water.  The  watery  extract  is  strongly 
acid,  and  has  the  characteristic  sour  smell  of  lactic  acid. 

(S)  Volatile  Acids  of  Butter.— Take  about  5  grms.  of 
butter,  and  treat  it  with  excess  of  strong  solution  of  caustic 
potash  in  alcohol,  warming  slightly.  When  the  action  is 
complete  drive  off  the  alcohol  in  the  water  bath  and  exhaust 
the  residue  with  a  little  water,  place  the  watery  extract  in  a 
retort  with  excess  of  phosphoric  acid  and  distil  gently.  Col- 
lect the  distillate  and  observe  its  odour  and  reaction. 


III. — Albumen  of  Egg  and  Serum. 

I .  Method  of  determining  the  temperature  of  coagulation. 

"A  glass  beaker  containing  water  is  placed  within  a  second 
larger  beaker  also  containing  water,  the  two  being  separated 
by  a  ring  or  cork.  Into  the  water  contained  in  the  inner 
beaker  there  is  immersed  a  test  tube,  in  which  is  fixed  an 


ALBUMEN.  59 

accurately  graduated  thermometer,  provided  with  a  long  nar- 
row bulb.  The  solution  of  the  proteid  of  which  the  tempera- 
ture of  coagulation  is  to  be  determined,  is  placed  in  the  test 
tube,  the  quantity  being  just  sufficient  to  cover  the  thermo- 
meter bulb.  The  whole  apparatus  is  then  gradually  heated. 
With  the  arrangement  described  the  rise  in  temperature 
takes  place  very  slowly  and  equally  throughout.  Care  being 
taken  to  have  as  good  illumination  as  possible  (the  best  plan 
being  to  place  the  apparatus  between  the  operator  and  a  well 
lighted  window)  the  experimenter  notes  the  temperature  at 
which  the  liquid  first  shows  signs  of  opalescence;  he  after- 
wards notes  again  the  temperature  at  which  a  distinct  separa- 
tion of  flocculent  matter  occurs," — Gamgee's  Physiol.  Chem., 
vol.  i.,  p.  15. 

2.  Dissolve  albumen  in  twenty  times  its  volume  of  ten  per 
cent,  salt  solution.  Introduce  some  of  the  liquid  into  a  loop 
of  dialysing  tube  (of  parchment  paper),  previously  tested  by 
filling  it  with  water,  and  suspend  the  tube  in  a  beaker  01 
water.  Test  the  external  liquid  from  time  to  time  for  chlo- 
rine, by  the  following  process : — 

3.  Estimation  of  Chlorine  in  the  Difiusate  -.—Dissolve  3*44 
grms.  of  pure  fused  silver  nitrate  in  distilled  water,  and  make 
up  the  solution  to  a  litre.  Dissolve  also  i  grm.  of  pure  fused 
sodium  chloride  in  water,  and  dilute  to  one  litre.  Fill  a  bu- 
rette with  the  silver  solution,  measure  with  a  pipette,  ten  c.c. 
of  the  sodium  chloride  solution,  and  place  it  in  a  beaker  with 
one  drop  of  a  solution  of  neutral  potassic  chromate.  Now 
run  in  the  silver  solution,  cautiously  stirring  the  mixture  dur- 
ing the  process,  until  the  red  colour  produced  by  each  drop 
of  the  silver  solution,  and  which  at  first  disappears  on  stirring, 
becomes  permanent.  If  the  solutions  have  been  accurately 
prepared,  ten  c.c.  of  the  silver  solution  corresponding  to  -o  i 
grm.  sodium  chloride  will  be  required. 


6o 


PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 


Construct  a  dialysing-  cell  by  closing  the  ends  of  a  length 
of  dialysing  tube  with  india-rubber  corks,  one  of  which  is 
perforated  for  two  glass  tubes.  Of  the  two  tubes  the  longer 
must  reach  to  the  lower  cork  and  be  bevelled  at  its  end  ;  the 
other  must  be  cut  off  short.  Through  this  arrangement  send 
a  current  of  water  from  the  tap.  Fill  a  narrow  cylindrical 
vessel,  not  much  larger  than  the  tube,  with  serum,  and  plunge 
the  latter  into  it.  Allow  the  water  to  flow  for  12  hours  and 
observe  the  precipitation  of  the  globulin. 

4.  Prepare  Lieberkiihn's  jelly,  by  adding  strong  potash  solu. 
tion  drop  by  drop  to  undiluted  white  of  egg,  stirring  vigorously; 
cut  up  the  jelly  into  small  pieces,  and  throw  it  into  a  large 
beaker  kept  full  of  water  by  an  arrangement  similar  to  that 
described  in  3.     Keep  the  produce  in  water  for  further  use. 

5.  Prepare  the  whites  of  two  eggs,  disintegrate  them  by 
clipping  with  scissors,  rinse  with  twenty  parts  of  water  by 
volume.  Introduce  the  mixture  into  a  corked  flask,  which 
must  not  be  more  than  half  full,  and  shake  briskly.  Strain 
through  muslin  and  filter. 

6.  Dilute  serum  of  blood  with  water,  so  that  the  mixture 
shall  have  as  nearly  as  possible  the  same  sp.  gr.  as  the  pre- 
vious one  (5). 

Compare  the  properties  of  the  two  forms  of  albumin,  ac- 
cording to  the  following  table  : — 


Serum  albumin  is  coagulated  be- 
tween 60°  C.  and  75°  C.  It  is  not 
readily  precipitated  by  hydrochloric 
acid.  The  precipitate  is  readily  sol- 
uble in  excess. 

The  precipitate,  by  boiling,  is 
readily  soluble  in  strong  nitric 
acid.  Its  solution  is  not  coagu- 
lated by  ether. 


Egg  albumin  is  coagulated  be- 
tween 63"  C.  and  70°  C.  It  is 
readily  precipitated  by  hydrochloric 
acid.  The  precipitate  is  not  read- 
ily soluble  in  excess. 

The  precipitate,  by  boiling,  is 
soluble  with  difficulty  in  strong 
nitric  acid.  Its  solution  is  coag- 
ulated by  ether  (if  the  solution  be 
not  alkaline). 


GLOBULIN.  6l 

IV.— Globulin  of  Serum. 

1.  Paraglobulin  or  Pibrinoplastin.— When  solid  magne- 
sium sulphate  is  added  in  large  excess  to  serum,  and  the 
mixture  violently  agitated  for  some  time  by  mechanical  means, 
a  dense  precipitate  is  obtained  (serum  globulin).  This  body 
is  an  example  of  a  class  of  proteids  which  are  distinguished 
by  being  insoluble  in  water,  soluble  in  weak  solutions  of  neu- 
tral salts,  but  insoluble  in  saturated  ones, 

2.  Collect  the  liquid  in  which  the  globulin  has  been  pre- 
cipitated, as  above  described,  on  several  filters.  It  will  re- 
quire many  hours  for  filtration.     Preserve  the  filtrate. 

3.  After  the  filtration  is  complete,  wash  the  filters  with  as 
little  water  as  possible,  this  will  rapidly  dissolve  the  precipi- 
tate. The  apparent  solubility  is  due  to  the  presence  of 
magnesium  sulphate. 

4.  Add  excess  of  magnesium  sulphate  in  powder  to  the 
clear  filtrate  from  (2).  It  becomes  turbid  when  shaken  for 
some  time. 

5.  Test  the  coagulation  point  of  the  liquid  as  before 
directed. 

The  Older  Methods  of  Separating  Serum  Globulin. 

6.  Panum's  method :— Dilute  serum  with  fifteen  times  its 
bulk  of  water,  and  add  four  drops  of  twenty-five  per  cent, 
acetic  acid  to  every  160  c.c.  of  the  mixture. 

7.  Alex.  Schmidt's  method :— Dilute  serum  with  twenty 
volumes  of  water,  and  pass  a  stream  of  COj  through  the 
mixture,  keeping  it  cool  during  the  process. 

8.  Collect  the  precipitate  on  a  filter  and  wash  it  with  water 
saturated  with  COj.     It  is  insoluble  in  water  that  has  not 


62  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

been  boiled ;     in  boiled  water  it   dissolves  with  great  diffi- 
culty. 

N.B. — An  additional  precipitate  may  be  obtained  from  the 
filtrate,  by  treating-  it  with  a  trace  of  acetic  acid.  This  was 
formerly  regarded  as  serum  casein  by  Panum. 

9.  Add  to  the  filtrate  from  3,  sodium  sulphate  in  powder 
in  excess,  a  further  precipitate  is  obtained.  This  is  serum 
albumin.  The  filtrate  still  contains  a  small  quantity  of  a  sub- 
stance which  gives  the  proteid  reactions. 

10.  Properties  of  Pericardial  Fluid :— Obtain  pericardial 
fluid  from  the  horse  slaughterers,  remove  the  contents  of  the 
pericardium  with  a  clean  glass  syringe,  choosing  for  the  pur- 
pose an  emaciated  animal,  and  taking  the  greatest  possible 
care  to  avoid  admixture  with  blood.  The  liquid  should  be 
clear,  and  of  a  pale  amber  colour. 

1 1.  If  freshly  collected,  it  either  fails  to  coagulate,  or  coa- 
gulates very  tardily.  Whether  it  coagulates  or  not,  it  yields 
when  treated  as  in  I  a  large  precipitate  of  globulin  similar 
to  that  of  serum. 

N.B.— If  hydrocele  fluid  can  be  obtained,  it  may  be  used  in- 
stead of  pericardial  fluid. 

12.  Coagulation  of  Blood-Plasma ;— Prepare  magnesium 
sulphate  plasma,  by  receiving  two  parts  of  horse's  blood  into 
one  part  of  a  saturated  solution  of  magnesium  sulphate. 
Great  care  should  be  taken  to  mix  the  liquids  thoroughly  im- 
mediately. The  mixture  must  stand  in  a  cool  place  (prefer- 
ably in  ice)  for  two  days,  to  settle.  After  subsidence,  the 
supernatant  liquid  must  be  carefully  drawn  off  with  a  pipette. 

13.  Collect  a  quart  of  horse's  blood  in  a  wide-mouthed 
stoppered  bottle,  and  set  it  in  ice  immediately.  After  it  has 
been  allowed  to  stand  for  two  days,  draw  off  the  serum,  and 
strip  off"  the  upper  colourless  stratum  of  the  clot  (buffy  coat), 
and  place  it  in  salt  solution. 


DIGESTION.  63 

14.  Dilute  some  of  the  magnesium  sulphate  plasma  with 
fifteen  to  twenty  volumes  of  water.  Place  it  in  the  warm 
chamber  at  3^°  C.     It  coagulates. 

15.  Mix  serum  with  pericardial  fluid  in  about  equal  volumes, 
and  treat  the  mixture  as  in  14. 

16.  Add  to  pericardial  fluid  in  a  watch-glass,  a  fragment 
of  fresh  buffy  coat,  and  place  it  in  the  warm  chamber.  Coa- 
gulation occurs. 


V. — Digestion. 

Natural  Digestion.— The  state  of  the  digestive  organs  dur- 
ing the  process  of  digestion,  can  be  best  seen  in  a  dog  which 
has  been  well  fed  with  meat  freed  from  masses  of  fat  some 
seven  hours  previously.  The  animal  may  be  conveniently 
killed  by  the  injection  of  cyanide  of  potassium  into  the  pleural 
cavity. 

I.  Open  the  abdominal  cavity  freely,  in  order  to  examine 
the  condition  of  the  lacteals  and  thoracic  duct.  Tie  the  stom- 
ach off  from  the  duodenum  by  two  ligatures,  dividing  between 
them  ;  do  the  same  at  the  lower  end  of  the  ileum.  Open  the 
stomach  along  the  greater  curvature,  turn  it  inside  out,  and 
collect  the  semi-solid  pulp  which  fills  it.  Observe  that  there 
is  very  little  liquid.  Dilute  the  contents  to  250  c.c.  with  water 
(if  the  dog  is  of  moderate  size),  strain  through  muslin,  and 
subsequently  filter,  precipitate  the  acid  liquid  by  boiling  with 
ferric  acetate.  (This  may  be  prepared  by  precipitating  a 
solution  of  iron  alum  with  lead  acetate,  allowing  it  to  stand 
overnight,  and  decanting  the  clear  liquid).  Filter  and  test 
the  filtrate  for  peptone,  with  alkaline  solution  of  cupric  hy- 
drate.    The  solution  should  give  no  precipitate  with  potassic 


64  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

ferrocyanide  and  acetic  acid.  The  same  method  may  be  ap- 
plied to  the  contents  of  the  intestine.  Note  the  absence  of 
foul  odour  and  (under  the  microscope)  of  bacteria. 

2.  Artificial  Digestive  Products.  — Gastric  Digestion.— 
Place  a  portion  of  mucous  membrane  scraped  off  the  stomach 
in  a  beaker,  with  02  per  cent,  hydrochloric  acid  at  38°  C.  in 
the  warm  chamber.  Observe  its  rapid  disappearance,  filter 
the  liquid,  and  test  its  digestive  power  by  the  method  de- 
scribed in  7. 

3.  Make  a  five  per  cent,  solution  by  volume  of  white  of  egg 
in  02  per  cent,  hydrochloric  acid,  add  to  it  glycerine  ex~ 
tract  of  stomach  in  the  proportion  of  lO  c.c.  to  the  litre. 
Leave  it  in  the  warm  chamber  for  twelve  hours;  neutralize^ 
separate  the  neutralization  precipitate  by  filtration,  boil  the 
filtrate  with  ferric  acetate  as  before  directed,  filter  and  test 
the  filtrate  for  peptone  as  before. 

4.  Pancreatic  Digestion.— Test  the  activity  of  the  gly- 
cerine extract  of  pancreas  by  the  method  described  in  Part 
III.,  IV. 

5.  Pound  part  of  an  ox's  pancreas  into  a  pulp,  place  it 
in  one  per  cent,  solution  of  sodium  carbonate  in  the  warm 
chamber,  and  allow  the  product  to  remain  in  the  warm 
chamber  for  several  days.  Strain  some  of  it  through  muslin, 
filter,  boil  the  filtrate,  and  again  filter.  Boil  the  second  fil- 
trate with  Millon's  reagent. 

6.  Apply  the  same  process  to  the  extract  of  the  intestinal 
contents,  and  compare  the  results. 

7.  Griitzner's  Method  of  Comparing  the  Digestive  Powers 
of  Solutions.— This  depends  upon  the  fact  that  when  fibrin 
stained  with  carmine  is  subjected  to  the  action  of  a  digestive 
ferment,  as  the  fibrin  is  dissolved,  the  carmine  is  liberated 
and  colours  the  fluid,  the  amount  so  set  free  being  estimated 


DIGESTION.  65 

by  an  artificial  scale  consisting-  of  ten  solutions  of  carmine  of 
different  strengths,  equal  quantities  of  the  stained  fibrin  being- 
mixed  with  equal  volumes  of  the  digestive  liquid  to  be  com- 
pared. 

The  following  materials  must  be  prepared  :  — 

I.  Carmine  solution  for  staining  the  fibrin;  take  i  grm. 
carmine  and  dissolve  it  in  about  i  c.c.  of  strong  ammonia, 
add  400  c.c.  of  water,  place  it  in  a  bottle  loosely  stoppered 
until  the  smell  of  ammonia  has  become  faint.  2.  Stained, 
fibrin;  take  perfectly  fresh  and  clean  fibrin,  chop  it  very  fine, 
place  it  in  carmine  solution  for  twenty-four  hours,  strain  off 
the  fluid,  and  wash  in  water  until  the  washings  are  colourless, 
squeeze  out  the  excess  of  fluid,  and  keep  in  a  stoppered  bottle 
with  just  enough  ether  to  cover  it.  3.  Another  solution  of 
carmine  to  serve  as  a  standard  of  colour.  This  is  made  by 
dissolving  i  grm.  of  carmine  in  ammonia  as  before,  and  dilute 
with  glycerine  to  100  c.c. 

Take  6  c.c.  of  solution  3,  and  dilute  to  60  c.c.  with  water. 
Charge  ten  test  tubes  with  quantities  of  the  mixture  ranging- 
from  I  to  10  cub.  centims.,  and  dilute  each  with  water  to 
20  c.c.  Cork  the  tubes  and  number  them  in  order,  according- 
to  the  strength  of  the  solution  it  contains. 

With  the  aid  of  a  measure  to  hold  i  c.c,  which  can  be 
made  by  closing  one  end  of  a  piece  of  glass  tubing-,  and 
grinding  the  open  end,  measure  out  two  equal  quantities  of 
stained  fibrin,  and  place  them  in  two  test  tubes  A  and  B,  each 
of  which  contains  20  c.c.  of  0-2  per  cent,  hydrochloric  acid. 
To  A  add  a  measured  quantity  of  one  digestive  liquid,  and  to 
B  precisely  the  sam.e  quantity  of  the  liquid  with  which  it  is  to 
be  compared.  Place  both  in  the  warm  chamber,  and  at  re- 
gular intervals,  which  must  be  carefully  noted,  compare  each 
(after  shaking)  with  the  colour  scale. 

r 


66  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 


VI. — Urine. 

1 .  Preparation  of  Urea  from  Urine.— Evaporate  the  urine 
to  a  small  bulk.  Add  strong  nitric  acid  (pure  and  free  from 
other  oxides  of  nitrogen)  in  excess,  keeping  the  mixture  cool 
during  the  addition  of  the  acid.  Pour  off  the  excess  of  fluid 
from  the  crystals  of  urea  nitrate  which  are  formed,  set  them 
on  a  porous  tile  or  perforated  dish  to  drain,  press  as  much 
fluid  from  them  as  is  possible.  Add  barium  carbonate  in 
large  excess,  mixing  thoroughly,  dry  on  a  water  bath  and  ex- 
tract with  absolute  alcohol ;  filter,  evapprate  the  filtrate  to  a 
syrup  on  the  water  bath,  and  set  aside  to  crystallize.  The 
product  may  be  further  purified  by  animal  charcoal  and  re- 
crystallization.  In  order  to  carry  out  this  process  properly, 
a  whole  day  is  required. 

2.  A  quicker  method  is  the  following.  Take  20  c.c.  of 
urine.  Add  "  baryta  mixture,"  (two  volumes  of  barium  hy- 
drate solution,  and  one  volume  barium  nitrate  solution,  both 
saturated  in  the  cold),  until  no  further  precipitate  is  produced; 
filter,  evaporate  to  a  thick  syrup  on  the  water  bath,  and  ex- 
tract with  alcohol.  Pour  off  the  alcoholic  extract,  filter,  and 
again  evaporate  to  dryness  on  the  water  bath,  and  take  up 
with  water.  Place  a  drop  of  the  watery  solution  on  each  of 
the  two  slides,  add  to  one,  strong  nitric  acid ;  allow  both  to 
crystallize,  and  examine  under  the  microscope. 

3.  Biuret  Reaction.— Heat  urea  to  150°- 160°  C.  Dissolve 
the  product  in  a  little  warm  water  and  add  a  solution  of  cupric 
sulphate  in  caustic  potash;  a  characteristic  violet  tint  is  pro- 
duced. 

3.  Dupre's  Method.  (See  Part  III.,  VIII.) — Urea,  when 
acted  upon  by  alkaline  hypobromites  or  red  fuming  nitric 


URINE.  67 

acid,  splits  up  into  carbonic  anhydride,  nitrogen,  and  water. 
Tiiis  decomposition  forms  the  basis  of  Dupre's  and  other 
methods  of  estimating-  urea  by  measuring  the  amount  of  ni- 
trogen produced  in  the  reaction.  In  this  method,  only  92  per 
cent,  of  the  nitrogen  of  the  urea  is  given  off.  Uric  acid  yields 
less  than  half,  the  other  nitrogenous  constituents  of  the 
urine,  variable  proportions  of  their  nitrogen,  Hippuric  acid 
is  not  decomposed.  In  the  graduation  of  Duprd's  apparatus 
this  error  is  taken  into  account. 

5.  Liebig's  Method..— A  solution  of  pure  mercuric  nitrate 
having  been  prepared,  of  such  a  strength  that  20  c.c.  of  it  are 
required  for  the  precipitation  of  10  c.c.  of  a  2  per  cent,  solu- 
tion of  urea, — of  which,  therefore,  10  c.c.  correspond  to  0"i 
grm.  of  urea  ; — add  20  c.c.  of  the  baryta  mixture  (see  2)  to 
40  c.c.  of  urine,  and  filter.  Measure  15  c.c.  of  the  filtrate, 
which  represents  10  c.c.  of  urine.  Place  it  in  a  beaker,  and 
run  in  the  mercury  solution,  (each  c.c.  of  which  corresponds  to 
O'Oi  grm.  of  urea),  until  on  mixing  a  drop  of  the  mixture  with 
a  drop  of  a  saturated  solution  of  sodium  carbonate  on  a  white 
tile,  a  pale  lemon  colour  appears.  Now  read  the  burette, 
and  calculate  as  follows  : — If  10  c.c.  of  urine  contained  0.2 
grm.  of  urea,  it  would  require  20  c.c.  of  the  mercury  solution. 
I.e.,  I  c.c.  for  each  grm.  per  litre.  If  the  daily  quantity  of 
urine  were  1500  c.c.  this  would  give  a  daily  discharge  of  30 
grms.  of  urea. 

This  method  approaches  accuracy  only  when  the  quantity 
of  urea  present  is  about  2  per  cent.  The  chlorine  in  the  urine 
must  also  be  estimated,  and  the  quantity  of  urea  indicated  re- 
duced by  the  subtraction  of  i  gramme  of  urea  for  every  13 
grms.  of  sodium  chloride  found. 

6.  Estimation  of  Chlorides  by  Liebig's  Method.— The  fol- 
lowing solutions  must  be  carefully  prepared,     a.  A  solution. 


68  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

of  mercuric  nitrate  of  such  a  streng^th  that  i  c.c.  shall  corre- 
spond to  •01  g'rm.  of  sodium  chloride.  Dissolve  20  grms.  of 
pure  mercury  in  boiling-  nitric  acid,  until  a  drop  of  the  acid 
fluid  does  not  cause  a  precipitate  when  added  to  a  solution  of 
common  salt ;  then  dilute  to  nearly  a  litre,  b.  A  solution  of 
pure  sodium  chloride,  20  ^rms.  to  the  litre,  c.  A  solution 
made  by  dissolving-  4  grms.  of  pure  urea  in  lOO  c.c.  of  diluted 
water,  d.  A  solution  of  sodium  sulphate  saturated  in  the 
cold. 

To  prepare  the  standard  mercuric  nitrate  solution,  place 
TO  c.c.  of  the  standard  sodium  chloride  solution  in  a  beaker, 
together  with  2  c.c.  of  the  urea  solution,  and  5  c.c.  of  the 
solution  of  sodium  sulphate.  Now  allow  the  solution  of  mer- 
curic nitrate  to  flow  g-ently  into  the  beaker  from  a  burette 
(with  glass  tap),  stirring  the  mixture  during  the  process.  A 
precipitate  forms  at  first,  and  is  redissolved  on  stirring.  On 
adding  more  of  the  mercurial  solution,  the  fluid  becomes  opa- 
lescent, but  no  permanent  precipitate  fcrms  until  the  reaction 
is  complete.  The  strength  of  the  mercurial  solution  having 
been  determined  by  several  experiments,  it  is  diluted  so  that 
20  c.c.  =  0-2  grm.  sodium  chloride  =  10  c.c.  of  the  standard 
sodium  chloride  solution. 

Precipitate  the  urine  with  baryta  mixture  as  directed  in  5. 
Take  15  c.c.  of  the  filtrate,  make  it  very  slightly  acid  with  very 
dilute  nitric  acid,  and  then  run  in  the  mercury  solution  cau- 
tiously, uniil  a  permanent  dense  cloud,  not  aff"ected  by  vigor- 
ous stirring,  makes  its  appearance ;  the  number  of  c.c.  used, 
multiplied  by  O'Oi,  gives  the  amount  of  chlorine  as  sodium 
chloride  contained  in  10  c.c.  of  urine. 

This  process  depends  upon  the  fact  that  when  mercuric 
nitrate  and  alkaline  chloride  in  solution  are  mixed,  sodium 
nitrate  and  mercuric  chloride  are  formed.     It  is,  therefore, 


URINE.  69 

not  until  all  the  chloride  in  the  urine  has  been  so  decomposed, 
that  mercuric  nitrate  begins  to  combine  with  the  urea  pre- 
sent, to  form  a  permanent  white  precipitate.  The  necessity 
for  estimating-  the  chlorides  when  using  Licbig's  process  for 
the  determination  of  the  urea  is  obvious. 

7.  Estimate  the  sug-ar  in  a  sample  of  diabetic  urine  by  the 
process  already  given  in  I.  7. 

S.  Uric  Acid.— Boil  serpent's  excrement  with  a  10  percent, 
solution  of  caustic  soda.  Dilute,  allow  the  liquid  to  stand, 
and  decant  the  clear  fluid  and  pour  it  into  a  large  quantity  of 
water  to  which  10  per  cent,  by  volume  of  hydrochloric  acid 
has  been  added.  Allow  it  to  stand  twenty-four  hours,  wash 
and  preserve  the  crystals  which  are  deposited. 

9.  Treat  uric  acid  or  a  urate  in  a  porcelain  dish  with  dilute 
nitric  acid,  and  evaporate  to  dryness;  after  cooling  allow  a 
drop  of  strong  potash  to  run  over  the  residue.  A  deep  pur- 
ple colour  is  produced. 

10.  Hippuric  Acid— Take  200  c.c.  of  fresh  cow's  urine  and 
concentrate  it  on  the  water  bath  to  iio  c.c,  add  Hydrochloric 
acid  and  set  aside  till  the  next  day.  Take  the  brown  crys- 
talline mass  which  forms,  wash  with  cold  water,  press  be- 
tween folds  of  filtering  paper,  dissolve  in  as  little  boiling 
water  as  possible,  add  a  little  pure  animal  charcoal  and  filter, 
concentrate  the  filtrate  and  set  aside  to  crystallize. 

11.  To  obtain  hippuric  acid  from  human  urine  take  (soon 
after  a  good  meal)  1  to  i'5  grms.  of  benzoic  acid  in  wafer 
paper.  Collect  the  urine  of  the  rest  of  the  day  and  following 
morning.  Evaporate  to  a  syrup  on  the  water  bath,  extract 
with  alcohol. 

12.  Dry  some  of  the  crystals  obtained  by  the  method  above 
given,  II,  between  folds  of  filter  paper  and  treat  in  a  test 
tube,  observe  that  a  red  oil  forms,   and  that  ammonia  and 


70     PRACTICAL  EXERCISES  IN  PHYSIOLOGY. 

benzoic  acid  are  given  off  as  may  be  recog"nized  by  the  smell. 
13.  Creatinin.— Precipitate  200  c.c.  of  urine  with  milk  of 
lime.  Filter  and  evaporate  to  a  syrup.  Extract  with  large 
excess  of  alcohol  and  filter.  Add  to  the  filtrate  tv^o  drops  of 
a  perfectly  neutral  solution  of  zinc  chloride.  Set  the  liquid 
aside  in  a  dark,  cool  place  for  two  or  three  days.  Creatinin 
zinc  chloride  crystallizes  in  rosettes,  in  vertical  lines  on  the 
sides  of  the  vessel. 


VII. — Urinary  Deposit. 

Urinary  deposits  may  be  divided  into  two  classes,  accord- 
ing to  the  reaction  of  the  urine  in  which  they  occur. 

I.  Deposit  in  acid  urine. — («)  The  so-called  lateritious 
deposit  which  forms  on  cooling  in  clear  healthy  urine,  of  high 
specific  gravity,  and  acid  reaction,  consists  chiefly  of  uric 
acid  and  urate  of  sodium,  coloured  by  the  urinary  pigments. 
This  deposit  may  be  obtained  from  any  acid  urine  by  slightly 
concentrating  and  allowing  it  to  stand. 

Allow  the  deposit  to  subside  and  decant  the  liquid  from  it. 
Examine  it  under  the  microscope.  If  uric  acid  is  present  its 
characters  can  readily  be  recognized.  Separate  the  crystals 
from  the  amorphous  deposit  of  urates,  by  washing  with  water, 
and  decantation.  Note  that  the  urate  is  readily  soluble  in 
warm  water,  especially  if  it  contains  a  trace  of  alkali. 

(d)  Calcic  oxalate  is  also  deposited  under  certain  conditions, 
in  acid  urine.  It  may  be  readily  recognized  by  the  micro- 
scope. To  observe  its  characters  add  to  warm  urine  a  few 
drops  of  solution  of  calcic  chloride  and  not  more  ammonium 
lOxalate  than  is  sufficient  to  produce  a  very  slight  precipitate. 


URINARY    DEPOSIT.  7I 

Allow  the  urine  to  stand  over  nig'ht.  After  the  ingestion  of 
any  considerable  quantity  of  rhubarb,  calcic  oxalate  is  always 
deposited. 

2.  Deposits  in  alkaline  urine.— (a)  Add  to  ordinary  urine 
a  few  drops  of  urine  which  is  already  ammoniacal,  and  allow 
it  to  stand  for  a  few  days  in  a  warm  place. 

The  deposit  is  whitish  and  consists  of  amorphous  basic 
phosphates  of  calcium  and  magnesium,  identical  with  the 
amorphous  precipitate  which  is  thrown  down  when  urine  is 
neutralized — along  with  which  are  seen  crystals  of  phosphate 
of  ammonium  and  magnesium  (triple  phosphate)  and  minute 
organisms,  on  the  surface  of  the  urine  is  a  scum  which  con- 
tains the  same  crystalline  and  organized  forms. 

(b)  Filter  ammoniacal  urine  (previously  decanted  from  the 
sediment)  wash  the  filter  and  dry  it,  then  dip  it  in  alcoholic 
solution  of  turmeric  and  dry.  The  paper  if  wetted  with  fresh 
urine  and  exposed  to  a  current  of  air  becomes  brown,  owing 
to  the  decomposition  of  the  urea. 

c.  Add  to  urine  ammonium  chloride  and  traces  of  sodium 
phosphate  and  magnesium  sulphate.  Urine  thus  treated 
yields  on  addition  of  ammonia  a  precipitate  which  on  stand- 
ing becomes  crystalline.  Compare  the  crystals  with  those 
obtained  from  ammoniacal  urine. 

d.  Acidulate  urine  with  acetic  acid,  then  add  calcium 
chloride  and  sodium  phos[)hate  in  relatively  small  quantities, 
A  precipitate  is  formed,  which  becomes  crystalline,  of  neutral 
calcic  phosphate.  This  body  is  precipitated  under  similar 
conditions  in  urine. 


72  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 


VIII. — Muscle. 

1.  Creatin,  from  aqueous  extract  of  muscle,  or  best,  from 
Liebig-'s  extract. — Dilute  the  latter  with  fifty  times  its  volume 
of  water  and  precipitate  it  with  lead  acetate,  excess  being 
avoided.  Filter,  separate  the  lead  by  sulphuretted  hydrogen 
and  again  filter.  Evaporate  to  small  bulk  and  set  aside  for 
a  week  to  crystallize.  Pour  off  the  mother  liquor,  and  add 
three  or  four  volumes  of  alcohol  sp.  gr.  0*982,  filter,  wash 
with  alcohol,  dissolve  all  the  crystals  obtained  in  boiling 
water,  again  filter  and  set  aside  to  crystallize.  Creatin  crys- 
tallizes in  transparent,  colourless,  rhombic  prisms,  for  which 
those  of  common  salt  may  be  easily  mistaken.  They  are 
distinguished  from  them  by  appearing  illuminated  in  the 
dark  field  of  the  polarization  microscope. 

2.  Sarkin  or  Hypoxanthin.— If  the  filtered  alcoholic  extract 
of  the  mother  liquor  of  creatin  be  evaporated  nearly  to  dry- 
ness on  a  water-bath,  extracted  with  water  and  filtered,  the 
filtrate  yields  on  the  addition  of  ammonia  and  ammoniacal 
solution  of  silver  nitrate,  a  precipitate  which  consists  of  silver 
compounds  of  hypoxanthin  and  xanthin.  For  the  method  of 
obtaining  these  bodies,  see  Gamgee's  Physiological  Chemistry, 

P-  329- 

3.  Acidification  of  Muscle.— (a)  Test  the  reaction  of  a 
fresh  sectional  surface  of  curarized  muscle.  For  this  pur- 
pose use  two  strips  of  glazed  litmus  paper  of  different  colours. 
Place  them  edge  to  edge  on  a  varnished  board,  and  affix  the 
cut  surface  over  the  junction.  The  reaction  is  neutral  or 
feebly  alkaline.  Test  it  again  half  an  hour  later,  it  will  be 
found  to  be  acid,  notwithstanding  that  the  muscle  has  been 
kept  in  a  moist  atmosphere,  or  under  mercury. 


BILE.  73 

(d)  Repeat  the  experiment,  keeping-  the  muscle  at  45"  C, 
observe  that  it  becomes  acid  much  sooner. 

(c)  Repeat  (a)  after  subjecting  the  muscle  to  prolonged 
tetanus.  This  is  accomplished  by  faradising  the  spinal  cord 
in  a  decapitated  frog,  after  previous  division  of  the  sciatic 
on  one  side,  and  comparing  the  reaction  of  the  cut  surface  of 
the  muscle  which  has  been  tetanized  with  that  of  the  other. 

4.  The  production  of  carbonic  acid.  That  this  process  is 
dependent  upon  contraction  may  be  shown  by  arranging"  two 
preparations  of  the  hind  limbs  of  a  frog  in  closed  vessels, 
over  lime  or  baryta  water.  Of  these,  one  is  continuously 
tetanized,  the  other  is  not,  and  air  (previously  deprived  of 
its  CO2  by  passage  through  strong  potash)  is  aspirated  slowly 
through  both.  If  the  experiment  be  continued  for  some  time, 
it  is  seen  that  much  more  carbonate  of  lime  or  baryta  is  de- 
posited in  the  vessel  containing"  the  tetanized  muscle  than  in 
the  other. 


IX.— Bile. 

1.  Mucin.— Add  to  bile  diluted  with  an  equal  volume  of 
water,  excess  of  alcohol.  Mucin  is  precipitated;  filter,  wash 
the  precipitate  with  dilute  spirit,  and  dissolve  in  lime  water 
and  again  filter.  Add  excess  of  acetic  acid  to  the  filtrate. 
Test  the  alkaline  solution  of  mucin  with  Millon's  reagent, 
nitric  acid,  normal  and  basic  lead  acetate. 

2.  Preparation  of  bile  crystals.— These  consist  of  a  mixture 
of  glycocholate  and  taurocholate  of  sodium,  and  are  to  be 
prepared  as  follows : — evaporate  the  bile  to  a  thick  syrup, 
and  extract  with  strong"  alcohol,  decolorise  the  alcoholic 
extract   with   animal  charcoal,    filter   and  evaporate  off  the 


74  PRACTICAL    EXERCISES    IN    PHYSIOLOGY. 

alcohol  on  a  water-bath,  extract  the  residue  with  absolute 
alcohol,  pour  the  solution  into  excess  of  ether,  and  set  aside 
to  crystallize  in  a  well-stoppered  bottle. 

3.  Taurin.— Boil  dried  or  inspissated  bile,  or  bile  crystals, 
for  some  time  with  strong  hydrochloric  acid  in  a  flask  fitted 
with  a  long  tube  for  condensing,  filter,  evaporate  to  dryness, 
extract  with  absolute  alcohol,  dissolve  the  residue  in  water, 
and  set  aside  to  crystallize. 

4.  Colouring  matters.— (a)  Take  dog's  bile,  acidulate  with 
acetic  acid,  add  excess  of  chloroform,  and  warm  gently ; 
remove  the  chloroform  with  a  pipette,  and  evaporate  on  a 
water-bath,  the  residue  is  crude  bilirubin. 

ib)  Extract  gall-stones  with  ether.  Keep  the  ethereal 
extract  for  the  cholesterin  it  contains.  Allow  a  few  drops 
to  crystallize  on  a  slide.  Examine  the  crystals  under  the 
microscope,  and  apply  the  iodine  and  sulphuric  acid  test. 
Boil  the  residue  in  water  acidulated  with  hydrochloric  acid  ; 
pour  off  the  bulk  of  the  fluid,  and  add  warm  chloroform. 
The  solution  on  evaporation  yields  crude  bilirubin.  Test 
the  solubility  of  the  product  in  water,  ether,  alcohol,  and 
chloroform.  Examine  the  solution  before  the  spectroscope, 
and  observe  that  it  shows  no  absorption  bands. 


X. — Glycogen  of  the  Liver. 

I.  Feed  a  rabbit  on  carrots,  and,  five  or  six  hours  after- 
wards, kill  it  by  opening  the  carotids.  Open  the  chest  and 
abdomen  quickly.  Insert  cannulse  into  the  vena  portse  and 
vena  cava  superior  respectively,  and  pass  a  gentle  stream  of 
water  through  the  liver  until  it  becomes  uniformly  pale.  Now 
cut  it  out  quickly,  mince  it,  and  throw  the  pieces  at  once  into 


GLYCOGEN    OF    THE    LIVER.  75 

boiling-  water  acidulated  with  acetic  acid.  Filter  the  liquid 
hot,  evaporfite  to  small  bulk,  and  add  large  excess  of  alcohol. 
The  glycogen  is  precipitated  as  a  flocculent  powder. 

2.  Take  the  livers  of  two  or  three  oysters,  mince  finely,  and 
throw  the  pieces  into  boiling  acidulated  water,  or  treat  as 
in  I. 

3.  Dissolve  a  small  quantity  of  glycog'en  prepared  as 
above,  in  water,  add  a  few  drops  of  saliva,  place  the  mix- 
ture in  the  warm  chamber  for  five  minutes,  and  test  for 
sugar. 


Printed  by  H.  K.  Lewis,  136  Gower  Street,  London. 


','''' 

'^. 


